The longitudinal Schottky spectra of a radio-frequency （RF） bunched and electron cooled 22Ne1~＋ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring （CSRe）, at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of Ap/p=l.6~lO-5 has been reached with less than 107 stored ions. The reduction of momentum spread compared with a coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25th, 50th and 75TM harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe.
Four types of magnetic alloy cores,labeled as V1,V2,A1 and A2,were produced by Liyuan Corp.Ltd.,for the radio frequency compression cavity of HIRFL-CSRm.In this work,their permeability,quality factor (Q value) and shunt impedance were measured before installing them into the cavity.The results show that the V1,V2 and A2 have higher permeability and shunt impedance,and lower Q value,and are suitable to the radio frequency compression cavity.
MEI LirongXU ZheYUAN YoujinJIN PengBIAN ZhibinZHAO Hongwei
The 400 MeV/u 12C6＋ ion beam was successfully cooled by the intensive electron beam near 1 A in CSRe.The momentum cooling time was estimated near 15 s.The cooling force was measured in the cases of difierent electron beam profiles,and the difierent angles between the ion beam and electron beam.The lifetime of the ion beam in CSRe was over 80 h.The dispersion in the cooling section was confirmed as positive close to zero.The beam sizes before cooling and after cooling were measured by the moving screen.The beam diameter after cooling was about 1 mm.The bunch length was measured with the help of the signals from the beam position monitor.The difiusion was studied in the absence of the electron beam.
The six species heavy ion beam was accumulated with the help of electron cooling in the main ring of Cooler Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). The ion beam accumulation dependence on the parameters of cooler was investigated experimentally. The 400 MeV/u 12C6+ and 200 MeV/u 129Xe54+ were stored and cooled in the experimental ring CSRe, and the cooling force was measured in different conditions.
Two types of pulse forming lines for dielectric wall accelerator （DWA） were investigated preliminarily. By simulation with CST Microwave Studio, the results indicate the pulse forming process, which can help to understand the voltage wave transmission process and optimize the line parameters. Furthermore, the principle of the pulse forming process was proved by experiments and some excellent pulse waveforms were obtained. During the experiments, the Blumlein line and zero integral pulse （ZIP） forming line, constructed with aluminum foil, poly plate and air gap self-closing switch, were tested. The full width at half maximum （FWHM） of the waveform is 16 nanoseconds （BL） and 17 nanoseconds （ZIP line）, and the formed pulse voltage amplitude is 5 kV （BL） and ＋2.2 kV/-1.6 kV （ZIP line）. The experiments result coincides well with the simulation.
In order to put the Pulse Line Ion Accelerator （PLIA） concept to its practical application, a small experimental platform was built. It was found that the actual axial electric field is smaller than the theoretical calculation, so the accelerated ions will enter into the deceleration zone before leaving the helix, which will seriously affect the acceleration process. Based on the improved parameters, the He＋ with 24 keV is accelerated to 55 keV, and the proof-of-principle experiment is completed on this platform.
