北京正负电子对撞机(BEPCⅡ)束流注入区辐射场研究
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摘要
北京正负电子对撞机(BEPCⅡ)正负电子束流注入阶段的束流损失,影响储存环束流注入区及防护区辐射场。本文利用束流损失监测系统(BLM系统)分析了束流注入阶段注入区束流损失的位置和束流损失率,并结合FLUKA软件模拟计算对撞实验模式下束流注入阶段注入区的辐射场。结果表明:注入阶段注入区及其下游束流损失明显;辐射场内粒子能谱情况是中子为宽能谱且各向同性,切割磁铁(铁靶)出射蒸发谱峰窄,峰值约为0.9 Me V,直接发射谱不显著;真空管(铝靶)出射蒸发谱峰宽且直接发射谱显著,峰值分别为4 Me V和20 Me V;光子能谱峰窄且前向性明显,能量在5 Me V以下分布集中;中子与光子剂量率水平相当;注入阶段比非注入阶段剂量率高约2个数量级;对撞实验模式下,实验测量整个运行阶段储存环光子剂量率平均水平约为1 000μSv/h,中子剂量率比光子剂量率低1个数量级。
When the beam is injected to the storage ring,the beam loss will influence the radiation field of beam injection zone and radiation protection zone. Using the beam loss monitoring( BLM) system to study the location and rate of beam loss,the results showed significant loss of beam in the injection zone and its downstream position. By the Monte Carlo simulation and experiment,the energy spectra of neutron and photon and their dose rates were obtained. When the beam is lost at the magnet,the peak of evaporation neutron spectrum is 0. 9 Me V and direct emission neutron are not obvious. When the beam is lost at the vacuum tube,the peak of evaporation neutron and direct emission neutron are 4 Me V and 20 Me V,respectively. The energies of photons are mainly below 5 Me V. The dose rates of neutron and photon are at the same level. The dose rate during the injection is about two orders of magnitude higher than that without injection. The dose rate of photon in whole stage of electron positron collision experiment is about 1 000 μSv / h,which is an order of magnitude higher than neutron dose rate.
When the beam is injected to the storage ring,the beam loss will influence the radiation field of beam injection zone and radiation protection zone. Using the beam loss monitoring( BLM) system to study the location and rate of beam loss,the results showed significant loss of beam in the injection zone and its downstream position. By the Monte Carlo simulation and experiment,the energy spectra of neutron and photon and their dose rates were obtained. When the beam is lost at the magnet,the peak of evaporation neutron spectrum is 0. 9 Me V and direct emission neutron are not obvious. When the beam is lost at the vacuum tube,the peak of evaporation neutron and direct emission neutron are 4 Me V and 20 Me V,respectively. The energies of photons are mainly below 5 Me V. The dose rates of neutron and photon are at the same level. The dose rate during the injection is about two orders of magnitude higher than that without injection. The dose rate of photon in whole stage of electron positron collision experiment is about 1 000 μSv / h,which is an order of magnitude higher than neutron dose rate.
引文
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[6]阎明洋,陈志,王遥,等.3 Me V电子辐照加速器通风管道辐射场计算[J].核技术,2013,(8):33-38.
[7]王庆斌,赵明,李建平,等.北京正负电子对撞机(BEPC)同步辐射实验西厅3W1光束线周围辐射剂量水平的测定[J].辐射防护,2001,21(3):176-181.
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[2]赵晓岩,曹建社,汪林,等.BEPCⅡ束流损失探测系统及其初步应用[J].中国物理C,2008,(S1):80-82.
[3]何俊,赵晓岩,汪林,等.BEPCⅡ束损系统研究[J].核技术,2015,10:15-21.
[4]National Council on Radiation Protection and Measurements.Radiological safety aspects of the operation of electron linear accelerators[R].NCRP Report No.188.1979.
[5]郑均正.《电离辐射防护与辐射安全基本标准》关于职业照射的控制[J].中国职业医学,2000,33(4):299-303.
[6]阎明洋,陈志,王遥,等.3 Me V电子辐照加速器通风管道辐射场计算[J].核技术,2013,(8):33-38.
[7]王庆斌,赵明,李建平,等.北京正负电子对撞机(BEPC)同步辐射实验西厅3W1光束线周围辐射剂量水平的测定[J].辐射防护,2001,21(3):176-181.
[8]Gaborit JC,Silari M,Ulrici L.Radiation levels in the CERN Large electron positron collider during the LEP 2 phase(68—105 Ge V)[J].Nuclear Inst and Methods in Physics Research A,2006,565(2):333-350.