cream - INFN

CREAM
Esperimento Struttura Flag Resp. Naz.
CREAM
PISA
1
CREAM_DTZ TORINO
EC4 ricalcolato
Allegato 1
Allegato 2
Allegato 3
File Not Found
http://www.lnf.infn.it/ac/preventivi/allegati/2003/PI_CREAM_All_3.pdf
http://preventivi1.infn.it:591/preventivi_2003/FMPro?-db=...p_naz_flag&-sortorder=descend&-sortfield=struttura&-find= [25-07-2002 19:40:21]
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Struttura
PISA
Ricercatore
responsabile locale: P. S. Marrocchesi
e-mail: [email protected]
Gruppo
2
Rappresentante
Nazionale:
P. S. Marrocchesi
Struttura di
appartenenza:
Siena
Posizione
nell'I.N.F.N.:
Incarico di Ricerca
e-mail:
[email protected]
PROGRAMMA DI RICERCA
A) I N F O R M A Z I O N I
Linea di ricerca
Laboratorio ove
si raccolgono i dati
Acceleratore usato
Fascio
(sigla e caratteristiche)
Processo fisico
studiato
Apparato strumentale
utilizzato
Sezioni partecipanti
all'esperimento
Istituzioni esterne
all'Ente partecipanti
Durata esperimento
Fisica astroparticellare. Apparato sperimentale per voli di lunga durata su palloni ULDB
(NASA) per la misura diretta degli spettri energetici e dell'abbondanza relativa degli
elementi chimici (fino a Z=28) presenti nei raggi cosmici primari ad energie fino a 1000
Antartide (lancio dalla base di McMurdo) + test-beams di calibrazione al Cern
raggi cosmici e fasci di test al CERN
raggi cosmici. Fasci di test al CERN (elettroni, adroni di energia 250 GeV)
meccanismo di accelerazione dei raggi cosmici in relazione alla variazione osservata
dell'indice spettrale (ginocchio) ad un'energia intorno a 3 - 5 10^15 eV
TCD (Timing Charge Detector) + odoscopi a fibre scintillanti per l'identificazione in carica
del primario e tracking; Transition Radiatio Detector (TRD); bersaglio di Carbonio;
calorimetro a Tungsteno e Fibre Scintillanti.
INFN-sezione di Pisa; Siena-Gruppo Collegato; sezione di Torino
Istituto di Fisica dello Spazio Interplanetario (IFSI) del CNR sez. di Torino, University of
Maryland, University of Chicago, Penn State University, University of Minnesota, Seoul
National University, NASA, NSBF
Primo periodo di presa dati 2003 - 2005 con voli a cadenza annuale
B) S C A L A
PERIODO
GENERALI
DEI
TEMPI:
piano di svolgimento
ATTIVITA’ PREVISTA
2003
Commissioning dell'odoscopio S2 per il primo volo; costruzione e beam test (CERN) del
calorimetro per il secondo volo (2004); studio upgrade elettronica di front-end (odoscopi);
programmi di simulazione e analisi
2004
Commissioning del calorimetro (entro Aprile 2004); calibrazioni (CERN) per il volo del
2005; analisi dati relativi al volo del 2003
2005
Contributo al commissioning del volo del 2005; analisi dati relativi al volo del 2003
Mod. EN. 1
(a cura del rappresentante nazionale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Resp. loc.:
Struttura
Gruppo
2
P. S. Marrocchesi
PISA
PREVENTIVO LOCALE DI SPESA PER L’ANNO
VOCI
DI
SPESA
2003
In kEuro
IMPORTI
DESCRIZIONE DELLA SPESA
Parziali
Totale
Compet.
A cura della
Comm.ne
Scientifica
Nazionale
4,0
riunioni della componente italiana della collaborazione
4,0
test-beam al CERN
riunioni di collaborazione /technical interchange meeting (USA +
CERN)
10,0
21,0
materiale di consumo per tests funzionali del calorimetro
sviluppo schede prototipali (upgrade elettronica di front-end)
metabolismo
3,0
10,0
2,0
15,0
2,0
2,0
trasporto del calorimetro al CERN per beam test
Consorzio
Ore CPU
Spazio Disco
Cassette
31,0
Altro
5,0
ADC-VME 32 canali
5,0
179,0
13,0
15,0
161,0
12,0
72,0
Tungsteno (471 Kg)
fibre scintillanti + fibre chiare + guide di luce
meccanica del calorimetro
fotorivelatori (HPDs) + elettronica (1/4 del totale)
materiale per costruzione odoscopio S2
fotorivelatori (HPDs) per odoscopio S2
Totale
452,0
509,0
Note:
Sono previsti interventi di edilizia e/o impiantistica che ricadono sotto la disciplina della legge Merloni?
Breve descrizione dell'intervento:
Mod. EN. 2
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Struttura
Nuovo Esperimento
CREAM
Resp. loc.:
Gruppo
2
P. S. Marrocchesi
PISA
ALLEGATO MODELLO EN 2
I fotorivelatori (HPD, proximity focused, 73 pixels) utilizzati sia nel calorimetro (40 +
spares), sia nell'odoscopio S2 (12) ed i relativi alimentatori hanno delle caratteristiche
tecniche che permettono il loro uso durante il volo ad una quota di circa 36 KM in condizioni
di sicurezza rispetto a breakdown discharge, corona effects etc.
Conseguentemente, il costo degli HPD e' elevato ed una riduzione di prezzo significativa si
puo' ottenere concentrando in un solo ordine la quantita' totale di fotorivelatori necessari.
Nella proposta CREAM, il profilo finanziario di spesa relativo ai fotorivelatoti e
all'elettronica
di front-end e' distribuito su due anni (2003-2004). Tuttavia, la
possibilita' di poter emetter un ordine unico per i fotorivelatori con scadenze di pagamento
dilazionate, porterebbe
ad un risparmio considerevole. Suggeriamo pertanto, in caso di
accettazione della proposta di CREAM, di autorizzare un unico ordine per gli HPDs basato su
un anticipo nel 2002 di circa 50 KEuro e con scadenze di consegne e pagamenti distribuite
opportunamente nel 2003 e nel 2004.
All. Mod. EN. 2
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Gruppo
2
Struttura
PISA
PREVISIONE DI SPESA: PIANO FINANZIARIO LOCALE
PER GLI ANNI DELLA DURATA DEL PROGETTO
In kEuro
ANNI
FINANZIARI
2003
2004
2005
TOTALI
Miss.
interno
Miss.
estero
Mater.
di
cons.
Trasp.e
Facch.
4,0
31,0
15,0
2,0
5,0
43,0
8,0
8,0
33,0
17,0
107,0
Note:
Mod. EN. 3
(a cura del responsabile locale)
Spese
Calcolo
Affitti e
manut.
appar.
Mat.
inventar.
5,0
Costruz.
apparati
TOTALE
Competenza
452,0
509,0
8,0
353,0
417,0
6,0
0,0
0,0
47,0
29,0
10,0
805,0
973,0
5,0
Osservazioni del Direttore della Struttura in merito alla
disponibilità di personale e di attrezzature:
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Gruppo
2
Struttura
PISA
PREVISIONE DI SPESA
Piano finanziario globale di spesa
In kEuro
ANNI
FINANZIARI
Miss.
interno
Miss.
estero
Materiale
di
cons.
Trasp.e
Facch.
Spese
Calcolo
Affitti e
manut.
appar.
Mat.
inventar.
Costruz.
apparati
TOTALE
Competenza
2003
7,0
35,0
15,0
2,0
5,0
452,0
516,0
2004
8,0
49,0
10,0
8,0
6,0
353,0
434,0
2005
8,0
33,0
6,0
0,0
TOTALI
23,0
117,0
31,0
10,0
47,0
11,0
805,0
997,0
Note: Il piano finanziario globale presentato si riferisce ai PRIMI TRE ANNI DI ATTIVITA' (2003-2005)
mentre il programma scientifico dell'esperimento prevede una serie di missioni a cadenza
annuale fino a coprire almeno 10 voli.
Mod. EN. 4
(a cura del rappresentante nazionale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Gruppo
2
Struttura
PISA
PROPOSTA DI NUOVO ESPERIMENTO
Lo spettro dei raggi cosmici primari segue una legge di potenza con indice spettrale pari a circa 2.7 per energie inferiori a 10^14
eV, ma presenta un indice spettrale piu' elevato a partire da un'energia vicina a 3 10^15 eV. L'osservazione sperimentale di un
cambiamento di pendenza, o "ginocchio" ("knee") nel flusso dei raggi cosmici alla scala di energia di 10^15 eV non ha ancora
trovato una spiegazione universalmente accettata a circa 40 anni dalla sua scoperta.
CREAM (Cosmic Ray Energetics And Mass) e' un esperimento, attualmente in fase di realizzazione, concepito per la misura
diretta dello spettro energetico e dell'abbondanza relativa di ciascuno degli elementi chimici (fino a Z=28) presenti nei raggi
cosmici primari UHE (da 10^12 fino a oltre 5 10^14 eV). La possibilita' di poter effettuare una misura significativa dal punto di
vista statistico e' legata al recente sviluppo, da parte della NASA, di una nuova classe di palloni Ultra Long Duration Balloon
(ULDB) progettati per voli di durata compresa fra i 60 e i 100 giorni con un payload scientifico fino a 1000 Kg e circa 400 W di
potenza.
In particolare, alcuni modelli prevedono un limite massimo all'accelerazione dei raggi cosmici da shock di supernova
[e.g.:Lagage, Cesarsky, 1983] con un cutoff nello spettro di energia a circa Z 10^14 eV. Secondo questa classe di modelli, lo
spettro inclusivo osservato sarebbe la sovrapposizione, pesata con le abbondanze relative degli elementi presenti nel raggi
cosmici primari, di spettri in cui la posizione del "ginocchio" avrebbe una dipendenza lineare con il numero atomico. La
determinazione sia della forma degli spettri esclusivi che delle abbondanze relative con misure dirette e' pertanto oggetto di
grande interesse scientifico. Questo richiede apparati sperimentali di grande accettanza, dato il modesto valore dei flussi attesi
a queste energie.
L'apparato sperimentale di CREAM include : un calorimetro a sampling in Tungsteno e fibre scintillanti preceduto da un
bersaglio di grafite di circa 0.5 lunghezze di interazione, con layers di scintillatori per il trigger e il tracking ; un Transition
Radiation Detector (TRD) e un identificatore (TDC) della carica del primario, basato su una tecnica di tempo di volo per la
reiezione del back-scattering dal calorimetro. Sara' il primo esperimento dedicato a misure di composizione dei raggi cosmici ad
essere dotato sia di un calorimetro che di un TRD. Misure simultanee dell'energia dei nuclei incidenti, identificati in base alla
carica, permettera' la calibrazione incrociata, durante il volo, dei due strumenti al fine di determinarne la scala di energia. Misure
ridondanti di carica con il TCD e con gli odoscopi di fibre scintillanti permetteranno un eccellente discriminazione in carica dei
singoli elementi (a basso Z) e dei principali gruppi chimici (ad alto Z).
CREAM e' stato approvato dalla NASA nel 1998 e, secondo l'attuale programma di sviluppo dei palloni ULDB, il primo volo
avra' luogo nel Dicembre 2003 dalla base di McMurdo in Antartide. I voli successivi avranno luogo con cadenza annuale.
Con un singolo volo, CREAM dovrebbe raccogliere una statistica circa doppia rispetto a quella attualmente accumulata da
esperimenti che hanno effettuato misure dirette dei cosmici primari con palloni nell'alta atmosfera con tecniche di rivelazione
basate su emulsioni nucleari (e.g.: JACEE, RUNJOB). Con 3 voli, l'intervallo di energie esplorato da CREAM avra' una
sovrapposizione di circa un ordine di grandezza con le misure indirette effettuate da esperimenti a terra e basate
sull'osservazione degli sciami nell'atmosfera. Questo permettera' agli esperimenti a terra una piu' accurata valutazione degli
errori sistematici legati alla determinazione simultanea dell'energia e della natura del primario a partire dall'osservazione
indiretta degli sciami.
La collaborazione CREAM include le seguenti istituzioni : University of Maryland, University of Chicago, Penn State
University, University of Minnesota, Seoul National University.
La partecipazione a CREAM da parte di gruppi INFN e' caldamente incoraggiata dalla collaborazione [Allegato 2] e il contributo
proposto ai gruppi italiani include la costruzione di un odoscopio a fibre scintillanti per il primo volo ULDB (2003), la costruzione
di un calorimetro per il secondo volo (2004) e la completa integrazione nelle attivita' della collaborazione sia nella simulazione
che nell'analisi dei dati sperimentali.
Informazioni piu' dettagliate sono incluse nella proposta di esperimento per il Gruppo 2 (Allegato 1 in formato .pdf) che puo'
essere consultata all'URL : http://www.pi.infn.it/~marrocch/cream/ alla quale si accede con username : infn ; password :
gruppo2 .
Mod. EN. 5
(a cura del rappresentante nazionale)
Pag. 1
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM
Gruppo
2
Struttura
PISA
PROPOSTA DI NUOVO ESPERIMENTO
Mod. EN. 5
(a cura del rappresentante nazionale)
Pag. 2
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Codice
Esperimento
CREAM
Resp. loc.:
Struttura
Gruppo
2
P. S. Marrocchesi
PISA
COMPOSIZIONE DEL GRUPPO DI RICERCA
Qualifica
RICERCATORI
Dipendenti
N
Cognome e Nome
Angelini Franco
Bagliesi M. Grazia (Siena)
2
Ciocci M. Agnese (Siena)
3
I Ric
Di Virgilio Angela
4
Ligabue
Franco
5
Maestro Paolo (Siena)
6
Marrocchesi P.S. (Siena)
7
Massai Marco M.
8
Meucci Mario (Siena)
9
10 Millucci Vincenzo (Siena)
11 Valle Giada (Siena)
Affer.
al
Assoc. Gruppo
Incarichi
Ruolo Art. 23 Ricerca
1
TECNOLOGI
R.U.
Dott.
R.U.
R.U.
AsRic
N
2
20
2
100
2
30
2
20
1
30
2
30
P.S.
2
60
R.U.
2
20
P.O.
2
50
P.A.
2
100
Dott.
2
30
1
Cognome e Nome
Qualifica
Dipendenti
Incarichi
Ruolo Art. 23 Ass. Tecnol.
Tecn
Morsani Fabio
50
1,0
Numero totale dei Tecnologi
Tecnologi Full Time Equivalent
TECNICI
N
Numero totale dei Ricercatori
Ricercatori Full Time Equivalent
Mod. EC/EN 7
Cognome e Nome
0,5
Qualifica
Dipendenti
Incarichi
Ruolo Art. 15 Collab.
tecnica
Assoc.
tecnica
11,0 Numero totale dei Tecnici
4,9 Tecnici Full Time Equivalent
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Codice
Preventivo per l'anno 2003
Struttura
Resp. loc.:
Esperimento
CREAM
Gruppo
2
P. S. Marrocchesi
PISA
COMPOSIZIONE DEL GRUPPO DI RICERCA
SERVIZI TECNICI
Denominazione
(a cura del responsabile locale)
Annotazioni:
Ingegnere meccanico (2 mesi uomo) : progettazione della versione finale (flight
mesi-uomo model) del meccanica del calorimetro.
MILESTONES PROPOSTE PER IL 2003 (a cura del responsabile nazionale)
Data completamento
Descrizione
1/03/1903
Commissioning dell'odoscopio a fibre scintillanti S2
1/10/1903
Costruzione e beam test (CERN) del calorimetro per il volo del 2004.
Mod. EC/EN 8
Resp. Naz.:
P. S. Marrocchesi
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM_DTZ
Struttura
TORINO
Ricercatore
responsabile locale: Andrea CHIAVASSA
e-mail: [email protected]
Gruppo
2
Rappresentante
Nazionale:
P.S. MARROCCHESI
Struttura di
appartenenza:
PISA
Posizione
nell'I.N.F.N.:
Incarico di Ricerca
e-mail:
[email protected]
PROGRAMMA DI RICERCA
A) I N F O R M A Z I O N I
Linea di ricerca
Laboratorio ove
si raccolgono i dati
Acceleratore usato
Fascio
(sigla e caratteristiche)
Processo fisico
studiato
Apparato strumentale
utilizzato
Sezioni partecipanti
all'esperimento
Istituzioni esterne
all'Ente partecipanti
Durata esperimento
Astrofisica particellare. Misura diretta dello spettro energetico e dell'abbondanza relativa
degli elementi(Z=1-28)primari fino a 5000 TeV
PALLONE STRATOSFERICO
ANTARTIDE (lancio da base Mc Murdo)
Raggi Cosmici e fasci di test al CERN
Raggi Cosmici e fasci di test al CERN (elettroni e adroni)
Origine ed accelerazione dei raggi cosmici tramite misure dirette dei singoli elementi e dei
loro spettri energetici.
TCD (Timing Charge Detector), TRD (transition Radiation Detectors), Odoscopi a Fibre
Scintillanti, Calorimetro W-Sci, Targhetta in Carbonio
PI-Siena(Gruppo Collegato)- TO
Istituto di Fisica dello Spazio Interplanetario del CNR - Sezione di Torino- Chicago U.Minnesota U. - Penn State U. - Seoul U. - NASA - NSBF
2003-2005
B) S C A L A
PERIODO
GENERALI
DEI
TEMPI:
piano di svolgimento
ATTIVITA’ PREVISTA
2003
Preparazione programmi di analisi e simulazione. Partecipazione ai test al CERN su
prototipo.
2004
Analisi dati del primo volo. Partecipazione ai test al CERN per il calorimetro.
Mod. EN. 1
(a cura del rappresentante nazionale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM_DTZ
Resp. loc.:
Struttura
Gruppo
2
Andrea CHIAVASSA
TORINO
PREVENTIVO LOCALE DI SPESA PER L’ANNO
VOCI
DI
SPESA
2003
In kEuro
IMPORTI
DESCRIZIONE DELLA SPESA
Parziali
Totale
Compet.
A cura della
Comm.ne
Scientifica
Nazionale
3,0
Riunioni di collaborazione e contatti con i gruppi partecipanti
3,0
4,0
Riunioni di collaborazione - Partecipazione test al CERN
4,0
Consorzio
Ore CPU
Spazio Disco
Cassette
Altro
Totale
7,0
Note:
Sono previsti interventi di edilizia e/o impiantistica che ricadono sotto la disciplina della legge Merloni?
Breve descrizione dell'intervento:
Mod. EN. 2
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Struttura
Nuovo Esperimento
CREAM_DTZ
Resp. loc.:
Gruppo
2
Andrea CHIAVASSA
TORINO
ALLEGATO MODELLO EN 2
All. Mod. EN. 2
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Nuovo Esperimento
CREAM_DTZ
Resp. loc.:
Gruppo
2
Andrea CHIAVASSA
Struttura
TORINO
PREVISIONE DI SPESA: PIANO FINANZIARIO LOCALE
PER GLI ANNI DELLA DURATA DEL PROGETTO
In kEuro
ANNI
FINANZIARI
Miss.
interno
Miss.
estero
Mater.
di
cons.
Trasp.e
Facch.
Spese
Calcolo
Affitti e
manut.
appar.
Mat.
inventar.
Costruz.
apparati
TOTALE
Competenza
2003
2004
3,0
4,0
3,0
6,0
2,0
6,0
17,0
TOTALI
6,0
10,0
2,0
6,0
24,0
Note:
Mod. EN. 3
(a cura del responsabile locale)
7,0
Osservazioni del Direttore della Struttura in merito alla
disponibilità di personale e di attrezzature:
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Codice
Esperimento
CREAM_DTZ
Resp. loc.:
Struttura
Gruppo
2
Andrea CHIAVASSA
TORINO
COMPOSIZIONE DEL GRUPPO DI RICERCA
RICERCATORI
Qualifica
Dipendenti
N
1
Cognome e Nome
Affer.
al
Assoc. Gruppo
Incarichi
Ruolo Art. 23 Ricerca
CASTELLINA Antonella
TECNOLOGI
CNR
2
N
Cognome e Nome
Qualifica
Dipendenti
Incarichi
Ruolo Art. 23 Ass. Tecnol.
30
Numero totale dei Tecnologi
Tecnologi Full Time Equivalent
TECNICI
N
Numero totale dei Ricercatori
Ricercatori Full Time Equivalent
Mod. EC/EN 7
Cognome e Nome
Qualifica
Dipendenti
Incarichi
Ruolo Art. 15 Collab.
tecnica
Assoc.
tecnica
1,0 Numero totale dei Tecnici
0,3 Tecnici Full Time Equivalent
(a cura del responsabile locale)
ISTITUTO NAZIONALE DI FISICA NUCLEARE
Preventivo per l'anno 2003
Codice
Esperimento
CREAM_DTZ
Resp. loc.:
Struttura
Gruppo
2
Andrea CHIAVASSA
TORINO
COMPOSIZIONE DEL GRUPPO DI RICERCA (cont.)
Annotazioni:
SERVIZI TECNICI
Denominazione
Mod. EC/EN 8
mesi-uomo
(a cura del responsabile locale)
Esperimento
gruppo
Rappresentante nazionale
Struttura res_naz
CREAM
2
P. S. Marrocchesi
Siena
ESPERIM.
Inviti
ospiti
stran.
Missioni
interno
Missioni
estero
Mater.
di
Cons.
Spes
Sem
Tras.
Aff. e
e Pub. Spese Manut.
Fac. Scien. Calc
App.
nuovo_continua
nuovo
Mater.
invent.
Costruz.
apparati
TOTALE
Personale
Ricercatori
FTE
1,0
0,3
Tecnologi
FTE
Tecnici
FTE
Rapporti (FTE/numero) Ricercatori
CREAM_D
TZ
Servizi mesi uomo
0,30 Ricercatori+Tecnologi
0,30
3
4
7
3
4
7
di cui sj
Totali
di cui sj
Richieste/(FTE ricercatori+tecnologi)
23,33
Personale
Ricercatori
FTE
11,0
4,9
Tecnologi
FTE
1,0
0,5
Rapporti (FTE/numero) Ricercatori
CREAM
Tecnici
FTE
Servizi mesi uomo
0,45 Ricercatori+Tecnologi
0,45
4
31
15
2
5
452
509
4
31
15
2
5
452
509
di cui sj
Totali
di cui sj
Richieste/(FTE ricercatori+tecnologi)
94,26
TOTALI
Totali
7
35
15
2
5
452
516
35,0
15,0
2,0
5,0
452,0
516,0
di cui sj
Confronto con il modello EC4
Mod. EC4 dati
Totali-Dati EC4
7,0
Personale
Ricercatori
FTE
12,0
5,2
Tecnologi
FTE
1,0
0,5
Tecnici
FTE
Rapporti (FTE/numero) Ricercatori
0,43 Ricercatori+Tecnologi
Richieste/(FTE ricercatori+tecnologi)
90,53
Servizi mesi uomo
0,44
07/11/02
INFN - Gruppo 2
Proposta per la partecipazione all'esperimento
CREAM
(Cosmic Ray Energetics And Mass experiment)
M.Aglietta (c), A.Di Virgilio (a), F.Angelini (a), M.G.Bagliesi (b), A.Castellina(c),
M.A.Ciocci, (b) F.Ligabue (a), P.Maestro (a), P.S.Marrocchesi (b), M.Massai (b),
M.Meucci (a), V.Millucci (a), F.Morsani (a, G.Valle (a)
(a) Univ. di Pisa / INFN Sezione di Pisa
(b) Univ. di Siena / INFN Gruppo Collegato
(c) Istituto Nazionale di Scienze Interplanetarie del CNR, Sezione di Torino
(1)
(2)
(3)
(4)
(5)
Inst. for Physical Science and Tech., University of Maryland, College Park, MD 20742, USA
Dept. of Physics, Penn State, University Park, PA 16802, USA
School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
Dept. of Physics, Seoul National University, Seoul 151-742, South Korea
Enrico Fermi Institute and Dept. of Physics, University of Chicago, Chicago, IL 60637, USA
ABSTRACT
CREAM (Cosmic Ray Energetics And Mass) is an experiment being constructed for a direct
measurement of Ultra High Energy cosmic rays (1012 to > 5 1014 eV) over the elemental
range from proton to iron, using the new Ultra Long Duration Balloon (ULDB) capability
under development by NASA. ULDB flights are designed to last from 60 to 100 days each.
CREAM includes a sampling Tungsten/Scintillating fibers calorimeter preceded by a graphite
target with scintillator layers for trigger and track-reconstruction, a transition radiation
detector (TRD) and a segmented timing-based particle-charge detector (TDC). It will be the
first experiment designed for high energy composition measurements to fly with a calorimeter
and a TRD. Simultaneous measurements of the energy and charge of a subset of nuclei, by
the complementary calorimeter and TRD techniques, will allow in-flight inter-calibration of
their energy scales. Dual charge measurements using the TCD and fiber hodoscopes will
allow excellent charge identification.
CREAM is expected to collect almost twice the current world total of direct high-energy
cosmic ray events in a single flight. With 3 flights the energy reach will overlap the low end
of the ground-based experiments range by almost an order of magnitude. According to the
current ULDB development schedule, the first launch from Antarctica will take place in
December 2003.
The partecipation of INFN to CREAM is warmly encouraged by the collaboration [Allegato
1] and the proposed contribution of the Italian groups includes the construction of a
scintillator hodoscope for the first ULDB flight (2003) , the construction of a calorimeter
module for the second flight (2004) and the full integration in the activities of the
collaboration including simulation and science data analysis.
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CREAM - Proposta al Gruppo 2 - INFN
07/11/02
Introduction
The spectrum of cosmic rays (CR) follows a power law with spectral index close to 2.7 for
14
15
energies below 10 eV, but it is considerably steeper for energies above 3 10 eV. The
observation of a change in spectral slope, or 'knee' in the fluxes of cosmic rays (Fig.1.1) near
15
energies 10 eV has caused much speculation since its discovery over 40 years ago. The
origin of this feature remains unknown, but it may suggest that more than one astrophysical
process is responsible for cosmic ray acceleration. The bulk of CR are thought to be
accelerated in galactic supernovae shocks. A class of models (e.g.: [1] Lagage & Cesarsky,
14
1983) predict both a cutoff at an approximate maximum energy of Z x 10 eV, where Z is
the particle charge, and an elemental composition of primary cosmic rays shifting towards
heavier elements at high energy.
Fig. 1.1 : All-particle energy spectra measurements
Direct measurements of primary cosmic ray energy spectra and of their elemental
composition up to the highest energies are the goals of a series of experiments planned to take
data in the next years. The aim is to understand the so far unknown mechanism of
acceleration of primary cosmic rays of very high energy [2], to identify their sources and to
clarify their interactions with the inter-galactic medium.
Measurements in this range of energies, performed to date (Fig.1.2) , can be divided into two
classes : direct detection by the balloon experiments JACEE [9] and RUNJOB [10],[11]
(nuclear emulsions) and indirect detection by ground-based air shower experiments including
KASCADE, CASA-MIA, DICE, BLANCA, SPASE-VULCAN and others (e.g.: HEGRA,
EAS-TOP ), the state-of-the-art in this field being summarized in the proceedings of the 27th
International Cosmic Ray Conference (2001) Hamburg [3].
Ground-based detectors observe the extensive showers of secondary particles initiated when a
primary cosmic ray interacts with a nucleus of the upper atmosphere. The interpretation of air
shower measurements depends on assumptions regarding the nature of the particles that
initiate the showers. Showers from heavier nuclei typically start higher in the atmosphere and
develop more rapidly than showers from lighter nuclei. Estimates of the primary composition
depend on parameters such as the depth of the shower maximum in the atmosphere and
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07/11/02
several other shower parameters, e.g., muon content. Energy estimates are affected by the
assumed composition of the primary particles.
Fig. 1.2 : All-particle energy spectra measurements near the `knee'
from various experiments from ref. [4]
Modern ground-based experiments exploiting the indirect detection techniques have many
more channels of information than in the past and simulation codes have become extensive
and sophisticated. However, the fact remains that determination of the identity of the nucleus
which initiates an air shower is a very difficult task. A fundamental limit seems to be
connected to the accuracy of the air shower models which are used to derive the composition
from the data. At present, the systematic errors in estimating the absolute energy scale and
shifts between the air shower models limit the accuracy in <log10(A)> to ~ 0.1. This is to be
compared with an expected shift of ~ 0.25 for a simple rigidity bend. There are mixed results
from this class of experiments for the existence of a simple bend in the spectrum [4]. While
the ground array measurements show a tendency for a heavier composition with increasing
energy, the air Cherenkov experiments show a tendency to lighten into the knee region with
some increase in mean mass beyond 3 PeV.
The detection of cosmic rays above the atmosphere is the only way to obtain direct
measurements of the primary particles and their energy spectra. There are a number of
techniques for direct detection.
The so-called "active" techniques usually involve some combination of charge detection and
energy measurement instruments, such as scintillator hodoscopes combined with a
calorimeter or transition radiation detector (TRD). Here, the data can be recorded
electronically in-flight and transmitted to the ground. Transition radiation detectors rely on
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the passage of a particle through the detector without a nuclear interaction while calorimeters
not only require an interaction but must contain as much of the hadronic shower as possible
for accurate energy measurements. The available calorimeter mass available for balloonborne or space-based payloads is an issue. Limitations on the calorimeter weight lead to the
development of the concept of Thin Ionization Calorimetry with the use of a low-Z target
preceding the calorimeter [6] as discussed in a later section.
Nuclear emulsion is an example of a "passive" technique that, when interleaved with suitable
converters, can simultaneously measure the primary charge and energy. These payloads must
be recovered and subjected to complicated and exacting procedures to extract the energy and
charge information.
While each technique has its own strengths and weaknesses, the major limitation to all direct
techniques to date is collection power. Due to the limited fluxes at high energy, largeacceptance detectors are required to collect a sufficiently large data sample within an
acceptable length of time. This limit is constantly being pushed as with the recent advent of a
new generation of baloons developed by NASA (ULDB) designed for 90 days flights and by
constructing payloads that do not require pressurized vessels for operation.
During the following years, direct detection experiments will be carried out by a series of
balloon flights. A dedicated large acceptance experiment ACCESS on the International Space
Station has been proposed [12,13,14] but not included among the last MIDEX missions
selected by NASA.
As the highest energy achievable in a balloon experiment is determined by exposure, the
experiments that will dominate the scenario in the next years fall into two categories :
•
•
LDB
: Long-Duration-Balloon (up to 3 weeks) flights (ATIC experiment)
ULDB : Ultra-Long-Duration-Balloon (up to 3 months) flights (CREAM experiment)
The Advanced Thin Ionization Calorimeter (ATIC) [15,16,17] Balloon Experiment is
designed to measure the composition and energy spectra of cosmic rays from ~10 GeV to
near 100 TeV utilizing a Si-matrix detector to determine charge in conjunction with a
scintillator hodoscope which measures charge and trajectory. Cosmic rays that interact in a
Carbon target have their energy determined from the shower that develops within a fully
active calorimeter composed of a stack of scintillating BGO crystals. ATIC's geometry factor
is about 0.25 m2sr.
The instrument was calibrated in September 1999 at CERN using accelerated electron, proton
and pion beams. ATIC was launched as a long duration balloon test flight from McMurdo,
Antarctica. A balloon launched during the astral summer from McMurdo travels in the polar
wind vortex which carries it around the continent, back to near the launch site, in 10-15 days,
providing a long exposure. After flying successfully for about 16 days in January 2001, the
ATIC payload was recovered in excellent condition. Preliminary results [17] were presented
on August 2001 at the 27th International Conference of Cosmic Rays (ICRC) - Hamburg.
Physics reach beyond 100 TeV will be an opportunity for CREAM [5,18,19,20,21,22]
designed to reach 500 TeV after a series of 3 Ultra Long Duration Balloon flights starting
from December 2003.
CREAM's geometry factor is about 0.5 m2sr for protons. Effective exposure for heavy nuclei
is greater than for protons due to their shorter interaction mean free path in the carbon target.
The effective geometry factors for heavy nuclei is 1.3 m2sr approximately.
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1.0
Physics reach
The primary science objectives of the CREAM experiment [5,18,19,20,21,22] are to:
•
•
•
Determine whether or not the spectral slopes of the heavier nuclei are the same as that
of helium and different from that of protons;
Measure potential changes in the spectra of secondary nuclei, and to
Search for spectral features, such as a bend in the proton spectrum.
These measurements will be able to verify whether the proton and helium spectral differences
that have been reported (e.g.: [7] Ellison et al., 1994) from combining all the existing data
sets are indeed real. Since the existing data were collected with several types of detectors,
including several different designs of emulsion chambers, some of the spread in the data is
undoubtedly due to systematic errors and differences in normalization among experiments.
Nevertheless, taking the data at face value, the proton and helium spectra appear to be
different at high energies (> 100 GeV/n), while helium has the same spectral shape as heavier
nuclei. This unexpected finding has received considerable attention, because simple shock
acceleration theory predicts the same power-law rigidity spectra for all species.
The effectiveness of CREAM to detect an abrupt change (kink) in the proton spectrum has
been illustrated in [5],[8]. The maximum kink energy that can be clearly observed as a
function of CREAM flight number is shown in Fig. 1.3.
Fig. 1.3 : Maximum kink energy that can be observed by CREAM as a function of flight
time assuming 100 days of exposure per flight.
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CREAM - Proposta al Gruppo 2 - INFN
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The curves correspond to a 2 σ significance level for two integral spectral indices, γ2 = 2.0
and 2.2, above the kink, where the index below the kink is γ1 is 1.7, i.e., for index changes of
0.3 and 0.5 at the kink [5 ].
CREAM has a larger collecting power than any instrument flown to date. The ultimate goal is
to accumulate at least 500 particles each for protons, Helium, CNO, Ne-Si, and Fe group
nuclei above 1014 eV. The payload would have to fly about 1000 days to reach 1015 eV with a
statistical accuracy of 30%. With 3 ULDB flights about 500 TeV would be reached.
A single CREAM ULDB flight would more than double the world’s current supply of high
energy (> 1 TeV) cosmic ray composition data.
Individual charge resolution and the energy response of CREAM will also allow a sensitive
measurement of secondary nuclei produced in the interstellar medium. At present these
measurements extend to around 100 GeV/n.
It seems unlikely that the strong energy-dependent decrease in propagation pathlength will
extend to the “knee” region since the residual pathlength at these energies would be
uncomfortably small [5]. CREAM can search for this change in the energy dependence out
to ~ 1 TeV/n, an order of magnitude above present data.
Given sufficient exposure on ultra-long-duration-balloon (ULDB) flights, the CREAM
instrument can meet or exceed the following measurement objectives:
−
−
Element Coverage:
Charge Resolution:
H to Ni (Z = 1 to 28), inclusive
Sufficient to resolve the 5 major element groups:
H, He, CNO, (Ar-Ni), with a desirable aim of resolving
individual species
−
Collecting Power:
−
−
Energy Calibration:
Energy Resolution:
0.3 m2-sr for Z 2 (considering interaction fractions);
1.3 m2-sr for heavier nuclei
Better than 30% absolute accuracy for energy calibration
Better than 50% energy resolution for each particle
CREAM is fundamentally different from other high energy composition experiments in that it
employs both TRD and calorimeter devices in the same payload. While both of these types of
detector have been flown before for high energy composition measurements, the combination
of instruments provides a powerful method to overcome the individual shortcomings of each
technique. A subset of nuclei will provide a response in both detectors that can be used to
calibrate the calorimeter energy scale against the TRD (the effective geometry factor for
events traversing the full instrument from the charge detector through the TRD to the
calorimeter and not interacting in the TRD but interacting in the target is about 70% ). Also
the calorimeter can detect protons and He for which the TRD can not reliably determine the
energy.
CREAM will provide a substantial overlap in energy with ground-based composition
experiments, which have thresholds near 1014 eV. This provides an important crosscalibration with the ground-based data. Direct measurements from CREAM will allow
predictions of cascade models of air shower parameters to be directly compared with a known
primary composition. This will provide confidence for extending direct composition
measurements to higher energies.
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07/11/02
2.0
CREAM configuration
The CREAM configuration, as shown in Fig.2.1, includes a scintillator Timing Charge
Detector (TCD), two TRD modules sandwiching a Cherenkov trigger layer, fiber hodoscopes
interleaved with graphite targets, and a sampling tungsten/scintillator calorimeter with fine
lateral segmentation.
Fig. 2.1 : CREAM instrument configuration
2.1
Timing Charge Detector (TCD)
The CREAM charge determination utilizes the fact that the incident particle enters the charge
detector before developing a shower in the calorimeter, while the albedo from the calorimeter
scatters back to the charge detector several nanoseconds later.
The TCD is comprised of two crossed layers of 0.5 cm thick, 30 cm wide, 120 cm long
paddles of fast scintillator, read out on both ends through 0.5 cm thick acrylic light-pipes by
fast photomultiplier tubes (PMT). Optical components are wrapped in black Tedlar for lighttightness. Light pipes are bent to reduce the TCD lateral dimension. The PMTs are read out
by fast, custom-designed timing electronics that measures both the slew rate of the rising
scintillation signal and the peak pulse-heights. With these two techniques the TCD electronics
cover the dynamic range required to identify vertically incident protons up to iron incident at
the highest angle within the CREAM geometry. The measured light-yield for cosmic-ray
muons through the center of the paddle is ~100 photoelectrons. Secondary particles scattered
back from the calorimeter can distort charge measurements. One way to reduce this effect is
through the use of finely segmented charge detectors to reduce the probability of a backscattered particle hitting the same detector component measuring the primary particle charge .
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07/11/02
CREAM - Proposta al Gruppo 2 - INFN
The Timing Charge Detector uses time separation instead of space separation. The worst-case
scenario is one in which the primary is incident on the center of a paddle and a particle backscattered from the calorimeter impinges on the same paddle near its end. If the primary
traverses the paddle at time t0, the scintillation light, traveling at an effective velocity of
approximately 0.6 c, arrives at the light-pipe at t0+3.3 ns. The primary, meanwhile, reaches
the calorimeter, 113 cm below, at t0+3.8 ns. The back-scattered particle reaches the paddleend at t0+8.0 ns, 4.7 ns after the signal from the primary. The TCD electronics are designed
to complete the charge measurement within 2 – 3 ns, thereby avoiding the impact of
background from back-scattered particles.
Under the graphite target (see below) is a fiber hodoscope read out by fast PMTs and frontend electronics identical to those of the TCD paddles. This hodoscope provides a reference
time, which allows the reconstruction algorithm to discard charge measurements for cases
where the primary missed the TCD and a back-scattered particle generated a TCD trigger.
This hodoscope is not used for pulse-height measurement of separate fibers, so signal
distortion due to particles traversing fibers outside the target geometry is not a concern and
clear fibers are not needed.
2.2
Transition Radiation Detector (TRD)
2
Each of the two TRD modules, with an active area of 120 x 120 cm , uses four active layers
in each transverse orientation. Each active layer is comprised of 32 thin-walled proportional
tubes. These tubes use a xenon-based gas mixture to detect x-ray transition radiation in the
energy region around 10 KeV. Adequate transmission of x-rays into the tube volume requires
very thin-walled devices. The CREAM TRD tubes use aluminized Mylar wound in three
layers and glued together to form a tube with a 75 µm wall thickness. A central sense-wire is
installed in each tube, which is operated as a conventional proportional counter to detect
ionization in the tube gas. The sense wire is held in place by end fittings, which also serve to
contain the gas mixture in the tube, at a constant pressure. The signal is amplified by an
analog system based on the Amplex VLSI charge amplifier chip. The tubes are held in a
polystyrene foam matrix. Each particle is measured by at least 6 tubes in each orientation. The
foam, aside from providing mechanical support for the tubes, generates the transition
radiation emitted by the charged primary particle as it repeatedly moves into and out of media
with different dielectric constants. The choice of radiator is optimized for Lorentz factors
from 103 to 104 . Since the number of TR photons is proportional to Z2 , TRD velocity
measurements are only possible for Z > 3, with expected energy resolution of ~15% for
carbon and 7% for iron at γ ~3000.
2.3
The calorimeter module
Limitations on the maximum allowed detector mass imposes severe constraints. Calorimeters
deep enough to allow nearly full containment of hadron showers are simply too massive to be
flown. A space-based hadronic calorimeter should be deep enough in both interaction length
(λint) and radiation length (X0) to generate interactions and contain EM showers produced by
secondary neutral pions, be light enough to fly and yet retain an acceptable geometric factor.
A workable compromise is provided by thin calorimeters with a light target (low-Z)
consisting of a 0.5 – 1.0 λint followed by a dense-absorber e.m. calorimeter at least 20
radiation lengths deep [6]. The rationale for this choice will be briefly summarized in the
following.
A proton incident on a block of matter interacts inelastically after 1 λint on average,
generating many secondary particles, mostly charged and neutral pions, in roughly equal
proportions. The neutral pions decay almost immediately into pairs of photons, initiating
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07/11/02
electromagnetic (EM) cascades. The target must force at least one hadronic interaction to
provide an energy measurement. A thickness of one interaction length of either a low-Z
material (e.g. C or Be) or high-Z material typically used in calorimeters (e.g. Fe, Pb, W, U,
BGO, etc.) provides similar interaction probabilities. However, a low-Z target with a smaller
value in g/cm2 requires less mass leaving a greater mass allowance for the calorimeter itself,
allowing greater lateral size and therefore increasing the effective acceptance. The latter
refers to particles in the detector’s geometric acceptance that also interact early enough to
allow their energy to be measured with sufficient accuracy.
A lower target density increases the overall stack thickness, but the impact on the effective
acceptance is much smaller. Another advantage of low-Z materials is the low ratio of λint to
X0 which minimizes the dependence of calorimeter response on the first-interaction depth.
An optimal solution for a space-based hadron calorimeter operating at very high energy is to
employ a high-density electromagnetic calorimeter preceded by a Carbon target.
Fig. 2.2 : conceptual scheme for a thin ionization calorimeter
A thin calorimeter of at least 20 radiation lengths can be built with dense absorbers (e.g., W
or U) where the physical depth of the calorimeter can be reduced to less than 10 cm. As
shown by MonteCarlo studies, this requirement can provide a sizeable improvement in the
target + calorimeter effective acceptance due to a better lateral containment for inclined
tracks.
Minimization of the maximum physical depth of the calorimeter can be easily achieved with
Tungsten (X0 3.5 mm) or Uranium while the use of a Pb absorber (X0 5.6 mm) would
result in a calorimeter with a stack depth almost twice as long. The better mechanical
properties of (sinterized) Tungsten and, on the other hand, the difficulties in the use of large
quantities of Uranium in space missions, greatly favour the use of Tungsten.
In addition to that, Tungsten (W) has smaller Moliere radius (ρM 9.0 mm) with respect to
Pb (ρM
16 mm) which implies the possibility of a smaller lateral granularity of the
calorimeter to improve the reconstruction of the shower axis in e.m. showers generated by
neutral pions in the hadronic cascade.
The performance of the CREAM calorimeter has been studied by simulating the detector
response using the GEANT + FLUKA 3.21 package. Protons have been generated
isotropically over an incident energy range from 100 GeV to 1 PeV (1015 eV).
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CREAM - Proposta al Gruppo 2 - INFN
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According to the simulated 1 PeV data, the maximum energy deposit in a single calorimeter
scintillator readout is expected to be less than 1 TeV, so the CREAM calorimeter electronics
is designed to cover the dynamic range from 5 MeV to 1 TeV.
The simulated longitudinal shower profiles for protons with incident energies up to 103 TeV
are shown in Fig. 2.3.
Fig. 2.3 : Longitudinal shower profile for incident energies from 0.1 to1000 TeV
The mean energy deposit, about 0.3 %, is found to be quite linear with the incident energy as
shown in Fig. 2.4 .
The energy resolution of thin calorimeters, driven by leakage, is crude by the standards of
ground-based devices, but sufficient for cosmic ray spectral measurements. The expected
energy resolution from the simulation is close to 42 % and quite independent of the incident
energy, as shown in Fig 2.5. These features are important for obtaining the true input spectra
by deconvolution, because they avoid bias in the spectral index measurements.
Fig. 2.4 : Mean deposited energy vs. Eincident
- 10 -
Fig. 2.5 : Energy resolution vs. Eincident
07/11/02
By extrapolating the reconstructed trajectory to the supplementary charge detector, the
entrance position of the primary particle is calculated. The deviation between the actual
incident position and the measured position is a Gaussian distribution with a sigma of about 1
cm. Position resolution is fairly independent of incident energy as shown in Fig. 2.6
Fig. 2.6 : Position resolution vs. incident energy
2.4
Target and scintillating fiber hodoscopes
The calorimeter is preceded by a 19 cm thick (~0.46 ? int) densified graphite target. This
graphite has a density of up to 2.1 g/cm3 (compared to 1.7 g/cm3 for typical industrial
graphite). The target flares out in the shape of an upside-down truncated pyramid with a slant
angle of 30°.
The target s divided into two elements cemented into composite cages and interleaved with 3
hodoscopes (Fig. 2.1).
Each hodoscope has two orthogonal layers of scintillating fibers (Fig. 3.3). Each multi-clad,
2 x 2mm2 square fiber is read out via a clear fiber (Fig. 3.4) of identical shape and lateral
dimensions, by a 73-pixel hybrid photo-diode (HPD). The clear fiber reduces the impact of
particles outside the target, where they cannot be filtered out by the graphite.
The top two hodoscopes (S0,S1), just below the lower TRD module, provide supplemental
charge measurement for particles already measured in the TCD. They also provide the only
charge measurement for the ~50% of calorimeter events that miss the TCD. A third
hodoscope (S2) is located between the targets. The three hodoscope systems also provide
tracking information.
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CREAM - Proposta al Gruppo 2 - INFN
3.0
07/11/02
Proposed INFN contribution to the CREAM instrument
In this section we describe, in more detail, the proposed contribution of the Italian groups in
terms of the construction and commissioning of scientific instrumentation flightware for
CREAM :
1. hodoscope S2 for the first flight ;
2. calorimeter module for the second flight;
3. contribution to the upgrade of the front-end electronics for S2.
According to the present time profile of the CREAM missions, an ULDB flight will take
place every year, starting from December 2003. Integration of the scientific paylod with the
ballooncraft for the second flight will take place during the Spring 2004, the second flight
being scheduled for the fall of 2004. Therefore, a second calorimeter module has to be built
and commissioned in time for the second flight. Assuming a series of successful missions, the
two twin calorimeters will fly on alternate years.
1. The partecipation of the Italian groups to the first flight is strongly encouraged by the
CREAM collaboration.
As described in the following Section 3.1 and chapters therein, people from INFN-Pisa
and Siena (Gruppo Collegato) built a reduced-scale S2 prototype which was successfully
tested with CERN beams in October 2001. We started a conceptual design study of the S2
flight module (see Fig. 3.1 and 3.2) in December 2001 and the construction (in early
2002) of a full-size prototype of S2, which is now ready in Pisa. Based on our experience
with both prototypes, we estimate that the proposed S2 hodoscope for the first flight could
be fully integrated with the CREAM instrument before the fall of 2002. The full
integration of the HPD read-out and relative tests could take place in the first quarter of
2003 followed by the delivery of the payload to NASA.
2. As described in following Section 3.2, the R&D project WCAL was financed by INFN
(Gruppo 5) for the construction and test of a W/Sci calorimeter prototype. The prototype
is being built in Pisa/Siena and will be tested at Cern in July/August 2002. The experience
gained in the design and construction of the prototype is the base for our estimates in
terms of cost and manpower for the proposed calorimeter flight model for the second
flight (Section 3.2.5).
3. The HPD baseline read-out for the CREAM scintillating fibers hodoscopes is designed
around an off-the-shell ASIC board containing two (32-channel) chip sets of the VA
family (IDE VA32_HDR2). An upgraded version of the front-end electronics for the
hodoscopes is under study. The aim is to achieve an enhanced dynamic range and reduced
noise (Section 3.1.3).
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07/11/02
3.1
The S2 hodoscope flight model
The S2 hodoscope is located in between the two targets sections T1 and T2. It consists of two
orthogonal planes of 2 x 2 mm2 scintillating fibers ( active area ~ 64 x 64 cm2). Each fiber is
connected to a clear fiber of identical cross section, with alternate fibers read-out by the two
Fig. 3.1 : S2 flight-model mechanics
opposite side of each plane. The clear fibers are routed, in groups of 64, to 12 HPDs (3 per
side). The path of the clear fibers, out of the target middle plane, takes place into 4 lighttight and light-weight boxes (one per side). Each group of 64 clear fibers is glued into an Al
mask ("cookie") which reproduces accurately the HPD pixels arrangement. After milling, the
Fig. 3.2 : S2 flight model light-tight boxes (view from the bottom of T2)
optical surface of the cookie is optically coupled to the HPD and pixels are aligned. The
alignment procedure of each cookie takes place by shining light simultaneously onto 3
different pixels, which are connected, via optical fibers to a blue LED. A view of the S2
boxes (from the bottom of the T2 target) shows the light mechanical structure of Al and
carbon fiber. Also visible are the 12 plastic "bellows" connecting the cookies to the 4 boxes.
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CREAM - Proposta al Gruppo 2 - INFN
3.1.1
07/11/02
The S2 reduced-scale prototype
In the framework of an R&D project (PRogetto di Interesse Nazionale) co-financed by the
University of Siena and INFN (sezione di Pisa), a small hodoscope prototype was built and
tested in a high energy beam at CERN in October 2001. The prototype consisted of 32 square
2 x 2 cm2 scintillating fibers covered by a 0.1 cm white EMA coating (Fig.3.3).
Fig. 3.3 : Scintillating fibers
Fig. 3.4 : Clear fibers routing to the MAPMT cookie
The active area was about 64 x 7 cm2. The scintillating fibers were glued head-on with clear
square fibers of the same cross section. Alternate clear fibers were routed, on opposite ends,
(Fig.3.4) to the 16 pixels of a MAPMT. The prototype (Fig.3.5) was read-out by 2 multianode photomultipliers HAMAMATSU - H6568 (Fig.3.6) .
Fig.3.5 : S2 reduced-scale prototype
Fig.3.6 : 16 pixel MAPMT cookie
The hodoscope prototype was first tested in our lab using a cosmic ray telescope (Fig.3.7) and
then it was exposed to CERN electron beams of energies between 5 and 100 GeV. A picture
of the test setup in the X7 beam-line is shown in Fig.3.8 (a).
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07/11/02
Fig.3.7 : Cosmic ray telescope used for the test
Pulse height spectra in Fig.3.8 (b) , recorded at a PMT gain close to 106 with a gated charge
integrating ADC, show a few fibers illuminated according to the beam profile. The MIP peak
is well separated from the noise.
During these tests the prototype was not equipped with fibers mirrored at one end. Further lab
tests were performed with single scintillating fibers, mirrored at one end, and coupled directly
to the MAPPMT in order to determine the average number of photoelectrons to be expected
as a function of the particle incidence along the fiber. Careful measurement of the position of
the single photoelectron peak with a blue LED allowed the calibration of the pulse height
scale. From the position of the MIP, measured under the same conditions, with the CR
telescope we obtained the average number of photoelectrons produced in the middle of the
fiber by a Z = 1 particle.
Fig. 3.8 (a) : S2 prototype at CERN beam
Fig. 3.8 (b) : Pulse height spectra from S2
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INSTITUTE F OR P H YSICAL SCIE NCE AND TE CH NOLOGY
College Pa rk, Ma ryla nd 207422431
301.405.4874 TEL 301.314.9363
FAX
301.314.9404 F AX
May 8, 2002
Professor Pier Simone Marrocchesi
Dipartimento di Fisica
University of Siena
55, via Banchi di Sotto - 53100 Siena - Italy
Responsabile del Gruppo Collegato INFN di Siena
Dear Professor Marrocchesi
On behalf of the Cosmic Ray Energetics And Mass (CREAM) collaboration, I am pleased to
invite you and your group to participate in our CREAM project. The goal of CREAM is to
measure the cosmic-ray composition to the supernova energy scale of 1015 eV using a series of
Ultra Long Duration Balloon (ULDB) flights, each having duration greater than about 60 days.
Our objective is to observe cosmic ray spectral features and/or abundance changes that might
signify a limit to supernova acceleration. CREAM is scheduled to be launched from Antarctica in
December 2003 for its first flight.
The extensive experience of your group in particle detector development will be very valuable
for the CREAM experiment. We are especially interested in your contribution to the development
of the S2 hodoscope for the first flight and the twin calorimeter section of the tungsten/scintillating
fiber layers for the second flight. The activities you proposed are important for this complex and
demanding cosmic-ray detector, and they would play a critical role in the success of CREAM. We
look forward to collaborating with your group in this significant contribution to precision particle
identification for our balloon-borne high energy cosmic-ray composition experiment.
Sincerely,
Eun-Suk Seo
CREAM Principal Investigator
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