Beam matching section in the new injector for RILAC

Abstract

The design and construction of the beam matching section of high frequency RFQ (Radio Frequency Quadrupole) linear accelerator and RILAC (RIKEN (The Institute of Physical and Chemical Research) Linear Accelerator) are described. The transverse beams were matched at two quadruple doublets, while the longitudinal ones were matched at rebuncher of fundamental frequency. The transverse beam matching was optimized with the TRANSPORT code. The magnetic field of quadrupole magnets was calculated using POISSON program. The dipole magnet was of the H type, and its parameters were optimized with the POISSON code. The longitudinal matching conditions were optimized by a transfer matrix method so that the output beam from RFQ could focus at the entrance of RILAC. All the geometrical parameters were optimized with the MAFIA code. The resonance frequency of the rebuncher resonator was measured, and it was found that these measured values were in good agreement with the values obtained by the MAFIA calculation. All the components were assembled in the RILAC beam line and it was confirmed that they worked properly. The vacuum stayed in the range of 2-4 x 10(exp -7) Torr during the operation. The transmission efficiency when the RFQ and the matching section were included was 40-50 percent in the first stage of the test.

RFQ(高周波)線形加速器とRILAC(理研線形加速器)のビームマッチング部の設計 と製作について述べた。ビームの横手方向のマッチングは2個の4極ダブレットを用い、長手方向のマッチングは基本周波数のリバンチャで行う。横手方向のビームマッチングはTRANSPORTコードを使い最適化した。4極磁石の磁場計算はPOISSONプログラムを用いて行った。双極磁石はHタイプでPOISSONコードを使い最適化した。長手方向のマッチング条件の最適化は、RILACの入口でRFQの出力ビームの焦点が合うように伝送行列法を用いて行った。MAFIAコードを使い、全ての幾何学的パラメータを最適化した。リバンチャ共振器の共振周波数を測定した。これらの測定値はMAFIAの計算結果と良く一致した。全ての部品をRILACビームラインで組み立て、正常に働くことを確認した。真空は運転中2〜4×10(exp -7)Torrで安定していた。RFQとマッチング部を含めると伝送効率は、第1段階の試験で40〜50%であった。