120203966
Beam loss distribution calculation and collimation efficiency simulation of a cooler storage ring in a heavy ion research facility
University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China(Received 18 November 2013; published 28 August 2014)The Heavy Ion Research Facility in Lanzhou is an ion cooler storage ring facility in China’s Institute ofModern Physics. The beams are accumulated, electron cooled, accelerated, and extracted from the maincooler storage ring (CSRm) to the experimental ring or different terminals. The heavy ion beams are easilylost at the vacuum chamber along the CSRm when it is used to accumulate intermediate charge stateparticles.Thevacuumpressure bumpduetotheion-induceddesorptioninturnleadstoanincreaseinbeamloss rate. Inorderto avoidthe completebeam loss, the collimation system isinvestigated and planned tobeinstalled in the CSRm. First, the beam loss distribution is simulated considering the particle chargeexchanged process. Then the collimation efficiency of the lost particles is calculated and optimized underdifferent position and geometry of the collimators and beam emittance and so on. Furthermore, the beamorbit distortion that is caused by different types of errors in the ring will affect the collimation efficiency.Thelinearizedandinhomogeneousequationsofparticlemotionwiththeseerrorsarederivedandsolvedbyan extended transfer matrix method. Actual magnet alignment errors are adopted to investigate thecollimation efficiency of the lost particles in the CSRm. Estimation of the beam loss positions andoptimization of the collimation system is completed by a newly developed simulation program.
64780564
Recent Progress of the SSC-LINAC RFQ
The project of SSC-LINAC RFQ has important progresses in the past year. The machine has been moved to the Institute of Modern Physics in the first season of 2013. The cavity measurement including tests of RF performance and field distribution is carried out again in the laboratory. The Q0 is 6440, and the unflatness of the electric field in longitudinal is ±2.5%. The results demonstrated a good agreement with simulation. The RF and beam commissioning of the RFQ has been carried out in the first half of 2014. The duty factor rose from 5% to CW gradually. By now, the cavity has been operated with 35 kW on CW mode. The measurement of the bremsstrahlung spectrum reveals that the 35 kW power is needed to generate the 70 kV inter-vane voltage. The beam transmission efficiency and energy spread has been obtained in beam commissioning by accelerating O and Ar beams. The efficiency of Ar is as high as 94%, and the output energy is 142.78 keV/u. All the processes and results of the experiments will be discussed in details.
118511112
A detailed study of the high-mass clump interacting with the bubble N10
We performed a detailed study of the high-mass clump interacting with bubble N10 based on the spectral lines 12CO(3–2), HCO+(4–3), N2H+(4–3) and CH3OH(7(0,7)–6(0,6)) and continuum emission data at 450 μm and 850 μm released by CADC and Spitzer. A blue-shifted optically thick line 12CO(3–2) seems to indicate that the outer envelope of the high-mass clump is still falling toward the center. Detection of CH3OH(7(0,7)–6(0,6)) suggests that a hot core has formed around YSO N10-7. The position–velocity diagram of N2H+(4–3) indicates that the cold dense core of the clump has not been destroyed by the star formation activities. The mass of N10-7 is about 27.44 M⊙. The ratio HCO+(4–3)/N2H+(4–3) in the outer part of the clump is larger than that in the inner part of it. The reason may be that the CO abundance relative to N2H+(4–3) is increased in the outer part of the high-mass clump, and more N2H+(4–3) were converted into HCO+(4–3).