positron

Paper	Title	Other Keywords	Page
MOP31	Development of a C-band Accelerating Module for SUPERKEKB	linac, klystron, acceleration, electron	108
	S. Ohsawa, M. Ikeda, K. Kakihara, T. Kamitani, T. Oogoe, T. Sugimura, S. Yamaguchi, K. Yokoyama KEK, Ibaraki
	High power rf processing of 1 m C-band accelerating section for Super KEKB was successfully performed and power corresponding to 42 MV/m was achieved. Processing data were accumulated including acoustic sensor to find the arcing position. No structural damage was observed from the phase shift measurement performed after the processing. Processed accelerator was installed in the beam line of KEKB linac and being re-processed. The beam acceleration of 40 MV/m was successfully achieved in October 2003. Present status of C-band accelerator development is reported.
MOP34	Injector Linac Upgrade for the BEPCII Project	electron, linac, target, gun	111
	S.H. Wang IHEP Beijing, Beijing
	BEPCII- an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requests its injector linac to have the higher beam energy (1.89 GeV) for on-energy injection and the higher beam current (40 mA e+ beam) for higher injection rate (≥50 mA/min). The low beam emittance (1.6 π·mm·mrad for e+ beam, and 0.2 π·mm·mrad for 300 mA e- beam) and low beam energy spread (±0.5%) are also requested to meet the storage ring acceptance. Hence the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and now being installed in their final positions, which are described in this paper. The beam commissioning is expected to start from the October of 2004.
	Transparencies
MOP37	Optimization of Positron Capture in NLC	target, electron, injection, emittance	120
	Y.K. Batygin SLAC, Stanford
	In the Next Linear Collider design, the positron capture system includes a positron production target, a flux concentrator, and a linac to accelerate positrons up to 1.9 GeV, the injection energy of the positron pre-damping ring. Two schemes for positron production have been studied: a conventional approach with a 6.2 GeV electron beam interacting with a high-Z target and polarized positron production using polarized photons generated in a helical undulator by a 150 GeV electron beam which then interact with a positron production target. The capture system has been optimized to insure high positron yield into the 6-dimensional acceptance of the pre-damping ring. Various parameters affecting the positron capture have been analyzed, including: positron deceleration after the flux concentrator, transverse and longitudinal electron beam sizes for positron generation, energy compression after acceleration, etc. As a result of these optimization studies, the positron yield in the conventional scheme has been increased from 1.0 to at least 1.5 and for the polarized positron scheme from 0.25 to 0.30 while maintaining 60% positron polarization.
	Transparencies
MOP38	Background from Undulator in the Proposed Experiment with Polarized Positrons	undulator, electron, background, photon	123
	Y.K. Batygin SLAC, Stanford
	E-166 is a proposed experiment for verification of polarized positron production for linear collider. According to polarized positron source design, high energy electrons pass through helical undulator and produce circularly polarized photons, which interact with tungsten target and produce longitudinally polarized positrons. In the proposed E-166 experiment, 50 GeV beam propagates inside 1m long undulator followed by a drift space of 35 m before interaction with target. Polarized positrons are analyzed by Si-W calorimeter, which is placed along the axis. Polarized positrons are analyzed by CsI calorimeter after reconversion of positrons to photons at the second target. Background is an issue for a considered experiment. GEANT3 simulations were performed to model production of secondary particles from primary electrons hitting undulator. Energy density distribution of background particles at the target and effect of background collimation are discussed.
MOP39	Positron Transmission and Polarization in E-166 Experiment	polarization, target, photon, focusing	126
	Y.K. Batygin SLAC, Stanford
	The proposed experiment E-166 at SLAC is designed to demonstrate the possibility of producing longitudinally polarized positrons from circularly polarized photons. Experimental set-up utilizes a low emittance 50 GeV electron beam passing through a helical undulator in the Final Focus Test Beam line of SLAC accelerator. Circularly polarized photons generated by the electron beam in undulator hit a target and produce electron-positron pairs. The purpose of post-target optics is to select the positron beam and to deliver it to a polarimeter keeping positron beam polarization as high as possible. Paper analyzes the positron transmission and polarization both numerically and analytically. The value of positron transmission has a maximum of 3% for positron energy of 7 MeV while positron polarization is around 80%.
MOP44	Electron-Cloud Effects in the Positron Linacs of Future Linear Colliders	electron, linac, simulation, acceleration	141
	D. Schulte, A. Grudiev, F. Zimmermann CERN, Geneva K. Oide KEK, Ibaraki
	Inside the rf structures of positron linacs for future linear colliders, electron multipacting may occur under the combined influence of the beam field and the electromagnetic rf wave. The multipacting could lead to an electron-cloud build up along the bunch train. We present simulation results of this effect for various proposed designs, and discuss possible consequences and eventual countermeasures.
	Transparencies
WE205	KEKB Injector Linac and Upgrade for SuperKEKB	klystron, linac, acceleration, injection	549
	S. Michizono KEK, Ibaraki
	KEKB Injector linac has provided the 8 GeV electrons and 3.5 GeV positrons to the KEKB asymmetric collider rings designed for the B-physics study. The KEKB has recorded the highest luminosity records to which the linac contributes with an advanced operational stability. The dualbunch injection and continuous injection schemes have been adopted. The operational status of the KEKB injector linac is summarized here. The Super KEKB project aiming for the ten-times higher luminosity is under consideration as the upgrade of KEKB. In this upgrade, the injector linac has to increase the positron acceleration energy from 3.5 GeV to 8 GeV. In order to double the acceleration field (from 20 to 40 MV/m), the C-band rf system has been tested. The newly developed components, such as an acceleration structure and an rf window, are summarized. A C-band acceleration structure is installed in KEKB linac after the rf conditioning of more than 40 MW. The energy gain of more than 40 MV/m is confirmed by the beam analysis. The C-band acceleration unit has been operated continuously for the stability test. The recent operational status of the c-band acceleration unit will be also reported.
	Transparencies
THP29	Development of C-band Accelerating Section for SuperKEKB	acceleration, linac, klystron, coupling	663
	T. Kamitani, N. Delerue, M. Ikeda, K. Kakihara, S. Ohsawa, T. Oogoe, T. Sugimura, T. Takatomi, S. Yamaguchi, K. Yokoyama KEK, Ibaraki Y. Hozumi GUAS/AS, Ibaraki
	For the luminosity upgrade of the present KEK B-factory to SuperKEKB, the injector linac has to increase the positron acceleration energy from 3.5 to 8.0 GeV. In order to double the acceleration field gradient from 21 to 42 MV/m, design studies on C-band accelerator module has started in 2002. First prototype 1-m long accelerating section has been fabricated based upon a design which is half scale of the present S-band section. High power test of the C-band section has been performed at a test stand and later at an accelerator module in the KEKB injector linac. In a beam acceleration test, a field gradient of 41 MV/m is achieved with 43 MW RF power from a klystron. This paper report on the recent status of the high-power test and also the development of a second prototype section.
THP61	SKIP - A Pulse Compressor for SuperKEKB	coupling, linac, acceleration, resonance	754
	T. Sugimura, M. Ikeda, K. Kakihara, T. Kamitani, S. Ohsawa, K. Yokoyama KEK, Ibaraki
	An upgrade of KEKB injector linac is planned. A main purpose of this upgrade is to increase injection energy of positrons from 3.5 GeV to 8.0 GeV for the SuperKEKB project. By a limitation of land area, our choice is to double an acceleration field utilizing a C-band accelerator structures instead of present S-band structures. Last year we developed C-band components such as accelerator structure, dummy load, 3 dB hybrid coupler, RF window, sub booster, modulator system, and so on. These components were assembled at a test stand and processed. This accelerator unit was installed in the beam line of injector linac and has been under operation. This summer we will install an RF pulse compressor system to the C-band accelerator unit. This paper reports the status of development of the RF pulse compressor system.