The worldwide largest UCN guide

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Forschungsneutronenquelle
Heinz Maier-Leibnitz (FRMII)
Technische Universität München
A UCN guide System for the FRMII
Dr. Thorsten Lauer - NDS 2015
Short intro in UCN business
Definition :
Ultra Cold Neutrons are totally
reflected at all incident angles by most
materials
Energy of neutrons in the
gravitational field of the earth:
E = mngh ~ 100 neV/m
Properties of ultracold neutrons:
energy
wavelength
velocity
temperature
lifetime
< 250 neV
> 55 nm
< 7 m/s
< 3 mK
15 min
Energy level splitting of neutrons
in a magnetic field:
 
V    B0  B  60.3neV / T
UCN can be stored in material or magnetic traps
Dr. Thorsten Lauer NDS 2015
UCN guide system for the FRMII
S-bend in UCN guide
Penelope
EDM
SR6 exit
UCN source
Biological shield
28 m
Sputtering Infrastructure at the FRMII
Vacuum chamber:
-
Length 3.6 m
Volume 243 liter
7.7E-7 mbar within 12 hours
Coating posibilities:
-
max. tube length 1.6 m
Max. diameter 180 mm
Two magnetrons installed
Targets available:
NiMo, NiV, Ni, Ti, Al, Cu, Cr, Au, C,
Gd, Ag
Successful coating
First of twelve UCN guides for test measurements at ILL
Optical wall potential NiMo
The measurements at MIRA
were performed by
K.Seemann and O. Soltwedel
UCN guide assemblies
Assembly of the final elements
UCN beam splitter
Guide characterization at ILL
Setup for transmission and storage measurements at PF2
-
Guide ID 115 mm OD 125 mm
-
Length per guide 1.5 m
-
Max. length ~17 m
-
In addition two 90° and one
25° bend in the beamline
-
3 self-made UCN shutters
-
Vacuum 3 x 10-6 mbar
UCN shutter system
Open shutter 0.5 mm gap
Closed shutter gap less than 0.03 mm
UCN leakage < 0.2 UCN/sec
Impressions of the longest UCN guide
2 x 45 ° bend section
90 ° bend section
pumping stations
selfmade shutters
Storage measurements
Storage measurement
in the whole guide
l 
Storage in a 1.5 m UCN
guide segment
4 Vguide
Aguide  v  
Storage time 40.5 sec
Storage time 42.1 sec
storage time behaves as expected
Almost no influence of the 0.1 mm slits between guides
Loss coefficient 
- With a slit between two guides of 0,1 mm
1
 eff

1


1

1
 sl  l
- τβ = 885 sec
4 Vguide

Aguide  v  l
- τeff = 40 sec
1/ 2
1/ 2
V
E
V  
 ( E )  2  arcsin     1 
V 
 E  
 E
- With a measured wall potential for NiMo
(85/15 wt%)
Vf = 221 neV
- for the total storage volume
  4.110 4
  2.73 10 4
   / 1.5
 eff


( Theor.
 2.5 10 4 )
effective storage time,  neutron lifetime, l losses due to absorption, up scattering…,
 sl slit losses
UCN guide transmission
Time of flight measurements
TOF spectrum 17 m
6 m/s
6 m/s
TOF spectrum 2.6 m
T: 0.499 ± 0.005
(0.992 ± 0.005) m-1
All people are happy…… BUT!
UCN Density
Turbine exit
After UCN guide
Density: 0.22/cm³
Density: 0.07/cm³
Conclusions:
- density reduces to 31.8% of the initial density
31.8 ± 1% (Density)
49.9% (Transmission)
Diffuse scattered neutrons
6 m/s
3,3 m/s
Transmission of only UCN (3,3 – 6 m/s)
0.327 ± 0.005
(0.961 ± 0.005) m-1
(0.318 ± 0.01 Density)
28m at the FRMII (straight) 33% transmission
transmissionsmessungen
Diffuse scattered neutrons
Simulations (by Geza Zgimond at PSI)
Simulations (by Geza Zgimond at PSI)
Simulations (by Yuri Sobolev in Mainz)
Labview front end:
- parameter control
- data handling
- Visualization
Visual C library:
- Simulation code
Simulations (by Yuri Sobolev in Mainz)
Ongoing work
A new cold,very cold and ultracold
neutron source at the TRIGA Mainz
starting Dec.2015
(TUM & IKCh Mainz)
Supermirror coatings for UCN applications….
Ongoing work
January 2016:
start of the MOVATEC GmbH (in Eching, Germany close to the FRMII)
-
UCN optics
Neutron Guides
Neutron Polarizers
…..
Wishes are welcome !
Forschungsneutronenquelle
Heinz Maier-Leibnitz (FRMII)
Thank you for your attention
And special thanks to the guide team 2014!

The worldwide largest UCN guide

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