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On October 10, Electron/Positron Injector Linac group successfully accelerated electron beams using a C-band accelerator section (5712MHz, 1m long) with an acceleration field of about 40 MV/m, which is twice as high as the current operational value. This result has demonstrated that the same acceleration energy as gained by presently-used accelerator structures (2856MHz, 2m long, 20MV/m) is obtainable by C-band structures at half length.
Since FY2002, the Linac group has been focusing on R&Ds of miniaturization and efficiency of electron linacs, regarding energy upgrade and stabilization of the Injector Linac. This is the first significant outcome and this technology is expected to be applied to upgrading of high-energy linacs and to miniaturization of linacs for medical or industrial purpose.
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Fig. 1 : One-meter C-band accelerator section installed in the fourth unit of the fourth sector (44) at Electron/Positron Injector Linac ( the right-side from the center). The left-side is an upstream direction, where part of 2-m S-band accelerator section (43) is also seen. The first measurement of the acceleration gain of the C-band accelerator section was successfully carried out, while the C-band accelerator section is now used to accelerate an electron beam for PF/AR(photon factory ring) as well. Several acoustic sensors are attached on the acceleration section in order to pinpoint the break-down location by detecting the vibration signal generated on the occasion of break-downs.
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Fig. 3 : First measurement of the acceleration gain in the 1-m C-band accelerator section. Beam energy variation was observed at the end of the linac by changing rf phases, giving an acceleration gain of 41.2MV/m, which is almost the design value.
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