A-RD-12Scintillating fibers detection system for
superconducting RF cavities
Y. Yamamoto on collaboration behalf
1TYL-FJPPL Strasbourg 10-12 May 2017
Enrico Cenni IRFU/CEA Yasuchika Yamamoto KEK
Juliette Plouin IRFU/CEA Kensei Umemori KEK
Hiroshi Sakai KEK
• First results during cavity vertical tests
• Future tests
• Summary
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Outline
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Experimental set-up
Test in CEA will be performed with:Scintillating fibers: BCF• -20 from Saint GobainPM Hamamatsu H• 10721-110
References:
D. L. • Chichester, S. M. Watson, and J. T. Johnson, Nucl. Sci. IEEE Trans. On 60, 4015 (2013).Saint • Gobain datasheet.S. Imai, S. • Soramoto, K. Mochiki, T. Iguchi, and M. Nakazawa, Rev. Sci. Instrum. 62, 1093 (1991).
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PMTScintillating fiber
Bremsstrahlung photons
Emitter
Top platePb
Pb
Electrons
Dose meter
Cryostat top view
PMT and shielding
Scintillating fiber
The fiber is positioned above the cover of the vertical cryostat.
Berthold micro-gamma LB112
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PMTScintillating fiber
Bremsstrahlung photons
Emitter
Pb
Pb
Electrons
Dose meter
During cavity vertical test we experienced some processing, theradiation dose dropped from 100µSV/h to 10µSv/h, at the sametime was observed a shift in the voltage.
100µSV/h
10µSV/h
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Rotating mapping system
Cavities testing area
We aim to compare PIN diodes measures with respect to scintillating fiber.
Possible configuration for the first test with PIN diodesFiber loop on 1. top flange with PIN diodes ring.
TOP FLANGE
PIN diodes
Scintillating fiber
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PIN diodes on G10 board adapted for the cavity beam pipe flange.
With a first test it will bepossible to measure andcompare the signal detected bythe PIN diodes and thescintillating fiber placed oncavity flange.
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A first test will be planned after summer in STF
2017 plan
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We plan to perform a measure with scintillating fibers introduced in the vertical cryostat •
along with PIN diodes (at STF-KEK).
We plan to measure scintillating response by means of standard radiation sources •
commonly use to calibrate scintillator detector.
Summary
We• have performed a first measure during cavity vertical test.
We• plan to continue tests during this year both in CEA and KEK
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Thank you for your attention
ご清聴ありがとうございました
Back up slides
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Understanding the problem:Different detection systems are currently used in order to measure x-ray produced by fieldemission electrons impacts.Commonly PIN diodes are placed on the cavity profile and/or scintillator detectors are placedoutside the cryostat during vertical tests.
PIN diodes provides a high spatial resolution while scintillator can provide dose rate and photonenergy spectrum .
Scintillating fibers offer benefit from both systems:• They can be installed close to the cavity surface High spatial resolution• They are scintillators Energy spectrum
With1. an x-ray map (location and energy) it is possible to determine the source position.During2. the machine operation will be possible to monitor any change in x-ray pattern.
Motivation
Case 2: energy spectrum measurement by NaI at cERL main linac cryomodule
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MotivationField emission issues:1. Field emission is one of the main issues for superconducting cavities quality factor
degradation at high gradient operation.2. Field emission electrons can induce material activation and damage accelerator
components.
Neutron yield with respect to electron energy.Cossairt, J. Donald. "Induced radioactivity at accelerators." FERMILAB-PUB-07-201-ESH. 2007.R. Geng (JLAB) @IPAC16
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Case 1: field emission study during vertical test (cERL main linac cavity)
8-9 iris(150 °)
tip (f a several 100um,a several 10um depth)
Result of X-ray mapping
330°
1cell
2cell
3cell
4cell
5cell
6cell
7cell
8cell
9cell
1-2iris
2-3iris
3-4iris
4-5iris
5-6iris
6-7iris
7-8 iris
8-9irisRotating mapping system
Array of Si PIN diode K. Umemori et al., IPAC10, WEPEC030, H. Sakai et al., IPAC10, WEPEC02816
Qo-Eacc・Maximum Eacc = 15 ~ 17 ・Eacc was limited by field emission・Large X-ray signals were observed
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Possible configuration for the first test with PIN diodesFiber loop on 1. top flange with PIN diodes ring.Fiber 2. along cavity profile or loop around an iris.
TOP FLANGE
PIN diodes
Scintillating fiber
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PIN diodes on G10 board adapted for the cavity beam pipe flange.
1st Test
With a first test it will bepossible to measure andcompare the signaldetected by the PINdiodes and thescintillating fiber placedon cavity flange.
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Possible configuration for the first test with PIN diodesFiber loop on 1. top flange with PIN diodes ring.Fiber 2. along cavity profile or loop around an iris.
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PMT
Scintillating fiber
X-ray
Field emission
He Tank
Location∝ Δt
tSi
gnal
References:
S. Imai, S. • Soramoto, K. Mochiki, T. Iguchi, and M. Nakazawa, Rev. Sci. Instrum. 62, 1093 (1991).
2nd Test
Two options will be available:1-Fiber loop on iris region (where signal is stronger)2-Fiber bundle along the cavity profile (on therotating mapping system)In both case will be possible to compare the signalfrom the fibers and the rotating mapping system. Amultichannel analyzer (MCA) will allow a measure ofenergy spectrum.
KEK rotating mapping system
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