Status WLSF Neutron Detector Prototype from Juelich

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Status WLSF
Neutron Detector Prototype
from Juelich
29. October 2013 | ZEA-2 – Electronic Systems | Ralf Engels and Guenter Kemmerling
Outline
• Measurement at HEIDI instrument
• Prototype of WLSF Detector Module
• Comparison between single and double ended fiber
readout
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• Conclusion
Measurements at HEIDI instrument
• Neutron wavelengths of 0.8 Å und 1.17 Å
• Transmission measurements with 3He-detector:
HEIDI 3He-Detector
 Scintillator with B4C-aperture in front of detector
 Absorption properties of different scintillators
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WLSF-Detectorprototyp
• Measurements with small WLSF-prototype:
 Development of neutron detection algorithms
 Determination of light yield, time characteristics,
detection efficiency, position resolution with two
fiber ends per pixel
Neutron Absorption Measurements @HEIDI
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He-3 Detector
Quality control of delivered scintillators
• tolerances of the delivered scintillators at
different compositions from two suppliers
• High number 6Li atoms result in the higher
absorption
• Sandwich-Layout with absorption of up to
~65% at 2:1 composition
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Comparison of AST and Eljen
•
Absorption measurements with
AST scintillators using different
thicknesses but the same
composition.
•
Absorption measurements with
Eljen scintillators with different
thickness and composition.
•
Squares are showing the same
scintillator at different wavelength
•
Squares are showing the same
scintillator at different wavelength
•
The colored curve is the
absorption calculation for different
wavelength with this composition
•
The colored curve is the
absorption calculation for different
wavelength with this composition
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Single and double ended fiber readout
Measurements:
•B4C-diaphrgam in neutron beam
Diaphragm with 2cm hole
Position reconstruction:
•Center-of-Gravity Method over
the illuminated WLSF
Absorption Efficiency for the WLSF Detector:
• Close to neutron absorption for the measured
scintillators
•Comparison with single and double ended fiber
readout with adequate results compared to
absorption
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Difference between one and two scintillators
In blue and red one can see
the different hits per plane
with only on scintillator. The
blue curve is the plane
located next to the scintillator
and red is the second plane
with less counts due to less
photons
Picture of the double
ended fiber readout
setup and the
orthogonal grid in front
but with no scintillator
In blue and red one can see
the different hits per plane
with two scintialltors on each
side. Here one can see no
different anymore while no
„shading“ effect
Position Reconstruction & Detection Efficiency (single)
Measurements:
•Single ended fiber readout
•B4C-diaphragm in neutron beam
•Diaphragm with 4mm holes and 10mm spacing
Position reconstruction:
•Center-of-Gravity Method over the illuminated
WLSF
•1,727 ±0,17 bin / mm pixel size in the diagram
•Reconstructed Peaks with FWHM of
δ_= 3,62 ±0,11 bin => δ = 2,10 ±0,06 mm =>
4,94 ±0,14 mm
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Detection Efficiency:
•Close to theoretical calculation
•Further data analysis will take place in the next
couple month
Results of WLSF test
measurements @HEIDI Feb. 2013
Position Reconstruction & Detection Efficiency (double)
Measurements:
•Double ended fiber readout
•Peak / Valley much better than single ended
•B4C-diaphrgam in neutron beam
•Diaphragm with 4mm holes and 10mm spacing
Position reconstruction:
•Center-of-Gravity Method over the illuminated
WLSF
•Reconstructed Peaks with FWHM of
δ_= 2,65 ±0,13 bin => δ = 1,62 ±0,08 mm
=> 3,81 ±0,18 mm
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Detection Efficiency:
•Close to theoretical calculation
•Further data analysis will take place in the next
couple month
Results of WLSF test
measurements @HEIDI Feb. 2013
„Big“ WLSF Prototype and next steps
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Detector module-Prototype tested :
•30 cm x 30 cm active area
•256 WLSF in total for X/Y- direction read out
by 4 MaPMTs from Hamamatsu
•First operation with neutrons from a
252Cf-source in 09/12,
•First successful operation with neutrons
@TREFF FRM II in 03/13
Block diagram of the Chip
based read out electronics
for one detector segment
Prototype structure
• 32 fibers per layer
• 1mm spacing between fibers
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•
•
•
•
H7546 Multi Anode PMT
MaPMT Adapter Board
MAROC board
Pre-FPGA Board
Fiber; double ended readout
Fiber grid with scintillator
MaPMT readout electronic for 64 channels
•
MAROC ASIC from Omega
 Variable gain preamplifier 0-4
 Fast bipolar and unipolar shaper (15 ns)
with discriminator for each channel
 100% trigger efficiency at 1/3 p.e
(= 50fC), Qmax = 5pC
 Slow shaper with 2 S&H for on-chip
Wilkinson-ADC
•
Benefits:
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 Correction of PMT non uniformity
 64 trigger outputs for photon counting
 Analog information for calibration
 Low Power Consumption: 5 mW/ch.
•
Total electronic with FPGA board and optical
link is in the commissioning phase at ZEA-2
Conclusion
• Absorption measurements at a certain wavelength from different supplier are
analyzed and double checked
• Measurements with small size prototype for determination of neutron event
characteristics and development of detection algorithm
• Prototype for detector module with 256 fibers has been tested at TREFF
based on a crate readout electronic for pulse analysis
• Comparison measurements between single and double ended fiber readout
has been tested an characterized
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• Readout electronic: Board design and fabrication for a 64 channel MaPMT
has been finished. The FPGA board is in the commissioning phase together
with the MAROC3 board.
• Further topics:
 Adaption of the readout to a MaPMT
 Event detection and total read out electronic need to be designed
 Detection algorithm
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Teamwork !!!
Thanks !