Proceedings of the 1st Annual Meeting of Particle Accelerator Society of Japanand the 29th Linear Accelerator Meeting in Japan (August 4 - 6, 2004, Funabashi Japan)

EXPERIMENTAL STUDY OF POSITRON PRODUCTION FROM SILICON
AND DIAMOND CRYSTALS BY AN 8-GEV ELECTRON BEAM
T.Suwada1,A), K.FurukawaA), T.KamitaniA), M.SatohA), T.SugimuraA), K.YoshidaA), H.OkunoB), K.UmemoriC),
J.HaraD), H.FujimotoD), R.HamatsuD), A.P.PotylitsynE), I.E.VnukovE), I.S.TropinE), R.ChehabF),
A) Accelerator Laboratory, High Energy Accelerator Research Organization (KEK),B) Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK),C) Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK),
1-1 Oho, Tsukuba, Ibaraki 305-0801, JapanD) Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji, Tokyo 192-0397, JapanE) Nuclear Physics Institute, Tomsk Polytechnic University, 634050, P.O.Box 25, Tomsk, Russia
F)
LAL, IN2P3-CNRS, Universite de Paris-Sud, Bat.200-B.P.34, 91898 Orsay, FranceAbstract
We measured positron-production efficiency from an axially-oriented single crystal target by 8-GeV channeling
electrons at the KEK electron/positron injector linac. The targets tested are silicon crystals with the thicknesses of 9.9,29.9 and 48.15mm, a diamond crystal with the thickness of 4.57mm, and their combinations with amorphous tungsten
plates. The crystal axis <110> has been aligned to the electron beam by a precise goniometer. The positron-production
efficiency in the momentum range of 10-30MeV/c was systematically investigated for each target by measuring thepositron yield generated in the forward direction with a magnetic analyzer. The result shows that the maximum positronproduction efficiency from the 29.9-mm-thick silicon and the 4.57-mm-thick diamond combined with amorphoustungsten are 6.1% and 2.9%, respectively, larger than that from amorphous tungsten at the momentum of 20MeV/c. In
such a light crystal target combined with amorphous tungsten, the total target thickness, which gives the maximum
positron yield, is clearly reduced in comparison with that of the amorphous tungsten alone. The result is also comparedwith our previous experiments for tungsten crystal targets.

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[1] R.Chehab, et al. ,PAC’89, Chicago, IL, p.283.

[2] T.Suwada, et al.,Proceedings of the 27th LinearAccelerator Meeting in Japan, p.105.

397

Proceedings of the 1st Annual Meeting of Particle Accelerator Society of Japanand the 29th Linear Accelerator Meeting in Japan (August 4 - 6, 2004, Funabashi Japan)

6
Diamond
Silicon1
Silicon2
Silicon3
Wc's

Pe+ =20MeV/c(a) Diamond crystal
5

Enhancement

Positron yield[arbitrary unit]

700
600
500
400

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185
82.5

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77.5

gle

[mr7572.5ad]

70
67.5

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le [mH ang

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%<7F42(a)Pe+ =20 MeV/c
Positron Production Efficiency [%]

1.4

0.08

DiamondRelative Positron Yield[arbitrary unit]

1.2
1
0.8
0.6
0.4
0.2

Diamond
Silicon1
Silicon2
Silicon3
Wc's
Wa'sSimulation

Pe+=20MeV/c

0.07
0.06
0.05
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0.03
0.02
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000-30-20-1001020

12345Target Thickness [X ]300

Rotational Angle [mrad]

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Positron Production Efficiency [%]Diamond
Silicon

Pe+=20MeV/c

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0.1

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0.045

0.04

0.035

0.03

0.6

3

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3.5

4

4.5

5

Target Thickness [X0] at Maximum Yield

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Pe+ =20MeV/c
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398