2006 Fiscal Year Final Research Report Summary
Basic research of high-brightness positron and x-ray sources utilizing single crystal
| Project/Area Number |
17540377
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
原子・分子・量子エレクトロニクス・プラズマ
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| Research Institution | High Energy Accelerator Research Organization |
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Principal Investigator |
SUWADA Tsuyoshi High Energy Accelerator Research Organization, Accelerator Laboratory, Lecturer (20236061)
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| Co-Investigator(Kenkyū-buntansha) |
FURUKAWA Kazuro High Energy Accelerator Research Organization, Accelerator Laboratory, Associate Professor (00190132)
SATOH Masanori High Energy Accelerator Research Organization, Accelerator Laboratory, Assistant Professor (90353367)
UMEMORI Kensei High Energy Accelerator Research Organization, Institute of Materials and Structural Science, Assistant Professor (60353364)
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| Project Period (FY) |
2005 – 2006
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| Keywords | Channeling radiation / Coherent bremsstrahlung / Positron source / Tungsten single crystal / Electron / positron linear accelerator / Positron generation / Single crystal target |
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| Research Abstract |
A new tungsten monocrystalline positron target has been successtully employed for generation of the intense positron beam at the KEKB injector linac in September 2006. The target is composed of a tungsten monocrystal with a thickness of 10.5 mm. Tungsten crystals of various thicknesses were developed at collaborating Tomsk POLYTECHNIC University. A series of experimental studies at KEK have been carried out to find out the optimum crystal thickness as a function of the incident electron energy. Several technological issues were studied concerning the mounting of the tungsten crystal into the positron production station at KEK, because the crystal axis<111> must be oriented to the direction of the incident electrons to within a few mrad. To achieve this precise orientation without any alignment devices, the target assembly was carefully fabricated based on X-ray Bragg-reflection measurements in terms of the crystal axis orientation. After establishing these techniques, the crystal target was installed at the operational positron source of the KEKB injector linac. A conventional tungsten plate with a thickness of 14 mm has been used previously, and the conversion efficiency (Nei^+ Ne^-), the ratio between the number of positrons captured in the positron capture section and the number of the incident electrons, was 0.20 (mean). By replacing the tungsten plate with the tungsten crystal, it increased to 0.25 ( mean). The increase of the conversion efficiency has boosted the positron intensity to its maximum since the beginning of KEKB operation in 1999. The crystal target has been used for the first time at a high-energy electron/positron linac, and thus, useful information on radiation damage and stability of the crystal target will be obtained through KEKB operation. We believe that this new method could be applied in the next generation of B-factories and e^+ e^- linear colliders.
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