A-RD-12Scintillating fibers detection system for

superconducting RF cavities

Y. Yamamoto on collaboration behalf

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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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