Reduction of transverse emittance growth in J-PARC linac DTL

J-PARCリニアックDTLにおける横エミッタンス増大の抑制

佐甲 博之   ; Wei, G.; 三浦 昭彦 ; 池上 雅紀*

Sako, Hiroyuki; Wei, G.; Miura, Akihiko; Ikegami, Masanori*

J-PARCリニアックビーム電流15mAにおいて、2台のバンチャーの振幅を設計値のそれぞれ120%と90%に設定することにより、DTL直後の水平,垂直方向エミッタンスはそれぞれ12%と10%減少させることができた。20mAにおいても同様にバンチャーの振幅を110%と80%に設定すると水平,垂直方向エミッタンスはそれぞれ12%と17%減少した。さらに15mAにおいてはMEBT1の最下流の四重極磁石磁場を20%増加させることにより、水平,垂直方向エミッタンスはさらに減少し、それぞれ0.171, 0.200mm mradとなった。

In J-PARC linac at 15 mA, horizontal and vertical emittance after DTL is reduced by 12% and 10%, respectively by setting the amplitudes of the first and second bunchers to 120% and 90% with respect to the designed settings. The resulting normalized horizontal and vertical emittance is 0.230 and 0.205 mm mrad. At 20 mA measured in Jan 2010, horizontal and vertical rms emittance is reduced by 17% and 10% respectively by setting the amplitudes of the first and second bunchers to 110% and 80% with respect to the designed settings. The resulting normalized horizontal and vertical emittance is 0.273 and 0.253 mm mrad. At 15 mA, we further investigated dependence of emittance on quadrupole magnetic field in MEBT1. With the most downstream quadruple magnet field at MEBT1 enhanced by 20% from the designed values, the emittance is further reduced to 0.171 and 0.200 mm mrad. These results are compared with the IMPACT simulation.