The boron neutron capture therapy (BNCT) clinical facility, developed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences, is based on an accelerator system that includes an ion source, a low-energy beam transport line, a radio-frequency quadrupole (RFQ) accelerator, and three high-energy beam transport lines. The RF system supplies RF power to the RFQ cavity, enabling proton beam acceleration to an energy of 2.787 MeV. It incorporates two 150 kW solid-state power amplifier (SSPA) units, a low-level radio-frequency (LLRF) control system, and a high-power RF transmission line, featuring a compact architecture and highly reliable operation. This paper describes the design, development, commissioning, and operational performance of the BNCT_02# RF system.

The China Spallation Neutron Source (CSNS) is designed and constructed by the Institute of High Energy Physics, Chinese Academy of Sciences. The construction of CSNS includes an 80-MeV Linac, a 1.6-GeV Rapid Cycling Synchrotron (RCS), two beam transport lines, a solid target station of 100 kW, three initial neutron instruments and other utility facilities. Based on limited funding and lack of experience in the high-power proton accelerator and the spallation target, the CSNS design was optimized to an advanced user faculty to fulfill the urgent user demand, with a high performance/cost ratio, and to have the capability for the CSNS phase two project (CSNS-II) to increase the beam power to 500 kW with less investment. The CSNS construction started in October 2011, and finished in March 2018 on schedule, and reached the acceptance parameters. Since then, CSNS has been operating efficiently and stably. In March 2024, the proton beam power on the target was increased to 160 kW. More than 1700 user experiments have been carried out so far, indicating a strong user demand. The design, construction and commissioning of CSNS are presented in this paper.

Although boron neutron capture therapy (BNCT) has been regarded as a curative therapy for aggressive tumors, the frequency of tumor recurrence and metastasis remains high mainly due to the adventitious nature of the immune response. Here, we explore the process of the immune response cascade after BNCT and find that the rate-limiting step is antigen presentation. To overcome this barrier, we develop a carrier-free nano-boron agent (BN-R837 @PVP), comprising hydrophilic 10B-boron nitride nanostructures loading with an immune agonist imiquimod (R837). The nano-boron agent can be internalized and cloaked into tumor cells and then following neutron irradiation, obtain the R837-loaded BNCT-shocked tumor cells (BTCs). When the BTCs are injected subcutaneously, the antigen pool and R837 are co-delivered into the draining lymph nodes, boosting immune responses as well as preventing R837 from entering the systemic circulation. This eventually results in significant inhibition of distal tumor growth and metastasis with a high rate of complete tumor regression in vivo. Moreover, memory T lymphocytes exist in these immunized mice and exhibit potent long-term anti-tumor.

Background Medium energy beam transport (MEBT) of the China Spallation Neutron Source matches the beam from RFQ to DTL. It is found in the beam commissioning that the fringe field effect of quadrupoles in MEBT has a great influence on matching. Purpose The aspect ratio of the quadrupoles is 1.67, which induces a strong fringing field effect, and the hard-edge model used in the design needs to be improved. Methods The slicing model was performed, and the accuracy of the quadrupole model was improved. Furthermore, to use the improved model online, based on the premise that the integral field of the quadrupole magnet remains unchanged, an equivalent transfer matrix was worked out to make the beam parameters consistent with the slicing model in the simulation. Results and conclusions In the machine study, with the new model, the beam parameters at the RFQ exit were measured, which is much closer to the RFQ design value. The MEBT lattice was redesigned based on the equivalent transfer matrix. With the new matched MEBT, the transmission rate of DTL reached 99.5% in the beam commissioning, which is increased by a factor of 3%.

The flow and heat transfer characteristics of supercritical fluid in a U-tube have an important influence on the safe operation of a moderator, and the variation of gravity direction is suitable for special working conditions of the moderator. In this study, the three-dimensional turbulence flow and heat transfers of supercritical liquid hydrogen in a U-tube were investigated at an Re number ranging from 16,425 to 54,750 under constant heat flux (q = 80 kW/m2). The total length of the U-tube was 1725 mm, which had an entrance length L/D of 23, with the inner diameter and wall thickness of D × δ = 10 × 2 mm. The finite volume method was adopted, and the grid independence was verified by the grid convergence index (GCI). The calculation results of three turbulence models (SST k-w, RNG k-ε, Standard k-ε) were compared with the corresponding experimental data to obtain the turbulence model with the smallest error. The convective heat transfer characteristics with different values of heat flux (q = 30 kW/m2~100 kW/m2), mass flow (G = 3 g/s~10 g/s), and gravity (gx, gy, gz) were compared. Meanwhile, the heat transfer characteristics of supercritical liquid and conventional liquid hydrogen were compared. The results show that Nu increased from 5 g/s to 10 g/s by 56.6%, and mass flow rate had a greater impact on the variation of Nu; when gravity direction was consistent with the flow direction of liquid hydrogen (gx direction), the Nu number inside the channel was 4.21% and 5.56% higher than that in gy and gz direction, respectively. Supercritical liquid hydrogen has a stronger heat transfer ability than conventional liquid hydrogen, of which the Nu number is 16.7% higher. This study can provide useful guidance for the design of flow and heat transfer of supercritical liquid hydrogen in a U-tube and its application in moderators. Furthermore, it provides reference technical values for thermal safety and thermal management of the target station to ensure its safe and stable operation.

Ventilation design of the scattering room and sample room in the Chinese Spallation Neutron Source (CSNS) is of great significance to maintain good indoor air quality and ensure the health of radiation workers. Based on the computational fluid dynamics (CFD) theory, the three-dimensional models of the scattering and sample rooms were established and fourteen layout schemes were simulated. Subsequently, the best schemes were selected among three typical layout schemes. On this basis, the paper presents research about the influence of changing the height of the outlet on the ventilation quality. The results show that the trend of numerical simulation is consistent with experimental data, which verifies the reliability of the numerical method. The change of the exhaust port position has an apparent influence on indoor ventilation, which reduces the air age by 4–27%. When the position of the outlet descends 0.5 m, the air age decreases by 2–11%, and this study provides guidance and suggestions for the design of the scattering and sample rooms.

中国散裂中子源(CSNS)是基于强流质子加速器的大科学装置,通过高功率质子束流轰击重金属靶产生高通量中子用于开展中子散射研究,CSNS是世界上第四台、发展中国家第一台脉冲型散裂中子源.CSNS包括高功率强流质子加速器、中子靶站和中子谱仪以及相应的配套设施等.加速器由80 MeV负氢直线加速器、1.6 GeV快循环同步加速器及相应的束流输运线组成.CSNS加速器是我国第一台中高能强流高功率质子加速器,本文将介绍CSNS加速器的设计、关键技术、设备研制以及束流调试过程和其中关键问题.

Boron Neutron Capture therapy（BNCT）is a safe and dual targeted radiotherapy technology,it offers a very satisfactory therapeutic effects for the treatment of malignant brain tumor and melanoma as well as a good response for the treatment of head-neck cancer,hepatic metastasis and so on. Accelerator-based boron neutron capture therapy（AB-BNCT）is of the advantage of precisely targeting,low side-effect,wide adaptability,small size,reasonable cost,and once for all,etc. In this paper,the designing of BNCT02 accelerator,which is the second accelerator dedicated to BNCT in our institute,is briefly introduced. Then,the designing,the manufacture and the commissioning of the ECR ion source for BNCT02 is presented in detail. At present,the beam with energy of 35 keV,a maximum pulse current of 40 mA and an average current larger than 20 mA is got from the ion source. The normalized rms emittance of the beam is measured smaller than 0.2 πmm·mrad under conditions of small low duty factor and low current. The ion source has been running stably over 48 hours without any breakdown in the testwhen the beam duty cycle is 80% and the average beam intensity is greater than 20 mA. The other opponents of the accelerator such as the RFQ,RFQ power coupler,RFQ power source,magnets and their power supplier are also developed.

Boron neutron capture therapy (BNCT) is regarded as a revolutionary means for high-accuracy cancer therapy with cell-level selectivity. It has unique therapeutic effects for some malignancies, such as glioblastoma multiforme. melanoma, recurrent head and neck malignancy. It can also be used for cancer treatment of deep organ, such as liver and lung. Even though its principle was proposed about 80 years ago. it has never been utilized in routine clinic therapy in hospital until 2020. BNCT, as a binary therapeutic method, greatly depends on both high-quality neutron beam and highly target-selective boron drug. Tumor killing in cell-level accuracy can be achieved only when the two elements work together and collaborate closely. To realize such therapeutic effect, BNCT sets high requirement on both neutron source and boron drug. The research on boron drug is related with multi-disciplines, such as chemistry, biology, medicine, radiology. pharmacy and physics. This article focuses on the neutron source for BNCT. Commonly, there are two types of BNCT neutron sources: reactor-based neutron source and accelerator-based neutron source. Up to now, almost all clinic trials of BNCT therapy were performed with the former. Due to limited resources of reactor neutron source, only less than 2000 cases BNCT treatments have been carried out in the world since BNCT method was invented. Thanks to the intense beam proton accelerator development, accelerator based neutron source can provide better beam quality. and especially important it can be installed in a hospital environment, which is essential for wide-range application of BNCT. In accelerator-based BNCT field, China has a sound base owing to more than 20 years research and development in high intensity neutron source for spallation neutron source and accelerator-driven subcritical system. It is meaningful work to transfer the related technology to accelerator-based BNCT (AB-BNCT). In this paper we will firstly introduce the demand for neutron beam specification recommended by IAEA. Then the difficulties in BNCT slow development in passing decades are reviewed. A new era of BNCT is coming and one can expect a prosperous future, owing to accelerator-based BNCT. The core technology of AB-BNCT is explored and recent research achievements on BNCT research and development in China are reported. Various types of accelerators now can be used for BNCT facility. including electro-static high voltage, cyclotron and RF linac. Their pro and con are reviewed. Majorly two kinds of neutron generation targets are utilized for BNCT. and the characteristics comparison of these two are analyzed. On the newly constructed BNCT research platform in China, new boron drug research and development work are conducted in many institutes, universities and pharmaceutical companies. And in recent, a new AB-BNCT facility is under construction for clinic trials in a hospital. So we can have an optimistic viewpoint for BNCT future in China.

为了保证BNCT速调管功率源系统安全稳定运行,并满足系统实时监测、快速响应、故障定位、易维护等要求,开发设计一套基于西门子PLC的联锁保护系统.该系统实时监测水冷、高压电源、撬棒等所有设备工作状态,同时根据速调管要求执行加电、故障联锁逻辑程序,并实现故障定位、状态显示.本文主要介绍控制系统总体方案设计、软硬件设计以及后期的联调测试情况.

中国科学院高能物理研究所建造了一台基于加速器的硼中子俘获治疗(BNCT)实验装置.射频功率源系统为352.2 MHz射频四极加速器(RFQ)提供高频功率,使束流离开RFQ时,其能量达到3.5 MeV.BNCT射频功率源系统主要包括速调管功率源、数字低电平控制系统、射频传输系统.本文介绍了BNCT射频功率源系统,主要包括物理需求、系统组成、关键设备、安装和调试.目前该装置已进行动物实验,加速器打靶束流功率4.3 kW,加速器射频功率源系统运行稳定.

This work addresses the neutronic design of a Beam Shaping Assembly (BSA) that is appropriate for a Accelerator-based Boron Neutron Capture Therapy (AB-BNCT). Instead of designing a moderator utilizing the IAEA-1223 recommendation and in-phantom figure of merit, in this work we study neutronics to decrease the out-of-beam dosimetry by employing radiobiological figures of merit to assess the beam quality. In particular, in the radiobiological probability model, we include two normal tissue cases, and accordingly optimize the thickness and cone angle of the collimator. Hence, in this study, for a large opening diameter, i.e., 10 cm, we use a small cone angle, which can decrease the out-of-beam dosimetry effectively. Accordingly, for a small opening diameter, i.e., 2 cm in this study, we employ a large cone angle to guarantee that the neutron flux is large enough. Our simulation results demonstrate that the neutronics optimization of the collimator is a tradeoff between the out-of-beam dosimetry and the neutron flux. From our findings, we conclude that upon considering radiobiological figures of merit, collimators with a tunable design shape are more appealing due to adapting to different treatment situations.

The China Spallation Neutron Source (CSNS) started operation from 2018 and now run at its design power. However, a problem was observed that the beam transmission of the linac was decreasing and the beam loss was increasing during the operation. With simulations and measurements, we found that a long longitudinal tail existed in the beam bunch output from the RFQ. And this tail caused the longitudinal mismatch in the following linac. After inhibition of the longitudinal tail in the beam bunch, the beam transmission in operation can keep stable. INTRODUCTION The layout of the CSNS linac is shown in Fig. 1. It consists of an Hion source, a 3 MeV RFQ, an 80 MeV DTL and several beam lines [1]. Table 1 shows the main parameters of the CSNS linac. The commissioning of the linac started from 2015. In January 2018, the last DTL tank has been commissioned and the Hbeam has been accelerated to the design energy of 80 MeV for the first time. The commissioning was performed with the peak current of 10 mA, the pulse width of 100 μs, and the repetition rate of 1 Hz. Figure 2 shows an overlay of Current Transform signals along the linac. After performing orbit correction, transverse matching, and model optimization, the beam transmission of the RFQ can be about 97% and that of the DTL can be about 100% (with 1% uncertainty). Figure 1: CSNS linac layout. Table 1: Main parameters of the CSNS linac Ion Source RFQ DTL Input Energy (MeV) 0.05 3.0 Output Energy (MeV) 0.05 3.0 80 Pulse Current (mA) 20 15 15 RF frequency (MHz) 324 324 Chop rate (%) 50 50 Duty factor (%) 1.3 1.05 1.05 Repetition rate (Hz) 25 25 25 Figure 2: Current Transform signals along the linac. BEAM TRANSMISSION DECLINE The CSNS facility started operation in September 2018. Now it runs at its design power 100 kW. However, a problem was observed in the operation. The beam transmission of the DTL might drop about 2~4% in the operation. Firstly, we thought the decline may due to the instability of magnet current or RF filed. After monitoring these parameters for a long time, they were found to be stable, but the transmission decline was still observed. Finally, we found out that the reason to this problem is beam instability from the ion source. The RFQ transmission was affected by the beam instability. And the beam parameters output from the RFQ were changed. As a result, the beam was mismatched while transporting in the DTL and then lost in the DTL. In our experiments, we found the DTL transmission decline was synchronous with the RFQ transmission decline, like showing in Table 2. Table 2: Measured Beam Transmission of the Linac Transmission (%) RFQ 83.4 94.04 96.85 DTL 95.88 96.36 98.00 BEAM MISMATCH The beam mismatch contains two aspects: transverse mismatch and longitudinal mismatch. We will analyse them by using measurements and simulations. Transverse Mismatch As shown in Fig. 3, the MEBT is used to match beam output from the RFQ to the DTL. The MEBT includes ten quadrupole magnets (Q1~Q10) for transverse matching, two 324 MHz buncher cavities for longitudinal matching, and various beam diagnostic instrumentation for beam diagnosis [2]. To do matching, it is essential to get the initial beam Twiss parameters output from the RFQ. Two sets of diagnostics are adopted to measure beam Twiss. Firstly, four wire scanners are place in the MEBT to measure beam profile. The beam sizes are calculated from profile data obtained at the measurement stations. Calculating the beam ___________________________________________ * Work supported by National Natural Science Foundation of China (11505201) † pengjun@ihep.ac.cn 12th Int. Particle Acc. Conf. IPAC2021, Campinas, SP, Brazil JACoW Publishing ISBN: 978-3-95450-214-1 ISSN: 2673-5490 doi:10.18429/JACoW-IPAC2021-THPAB185 THPAB185 C on te nt fr om th is w or k m ay be us ed un de rt he te rm s of th e C C B Y 3. 0 lic en ce (© 20 21 ). A ny di st ri bu tio n of th is w or k m us tm ai nt ai n at tr ib ut io n to th e au th or (s ), tit le of th e w or k, pu bl is he r, an d D O I 4134 MC4: Hadron Accelerators A08 Linear Accelerators Twiss parameters is done using beam sizes and an envelope model. The beam Twiss parameters are found numerically by minimizing the RMS error between the measurements and the model predictions, as shown in Fig. 4. Table 3 shows the comparison of the design values (with PARMTEQM) and the measured values [3]. The Twiss parameters in the horizontal plane are agreed well with the simulated values, while those in the vertical plane are obviously deviated from the simulated values. Figure 3: Layout of the CSNS MEBT. Figure 4: Beam RMS size along the MEBT (Lines represent model predictions, and dots represent measurements with wire scanners). Table 3: Twiss Parameters at the MEBT Entrance α β (mm/ π mrad) ε Norm.rms (π mm mrad)

2020年1月19日敬爱的老师方守贤院士永远地离开了我们,大家再也听不到他洪钟般爽朗的笑声.由他开拓的加速器驱动洁净核能系统(ADS)研发事业,正在我国有声有色地强劲发展.作为学生,我以此短文,追忆方先生当年指导我们开展ADS研究的一些往事,以此缅怀先生对我国科技事业的杰出贡献.

*Work supported by Youth Innovation Promotion Association of CAS (2015011) † email address:liuhc@ihep.ac.cn OPERATION EXPERIENCE OF THE CSNS DTL* Huachang Liu1,2,3†, Jun Peng1,2,3, Keyun Gong1,2,Ahong Li1,2,3, Bo Li1,2, Qiang Chen1,2, Xiaolei Wu 1,2 ,Mengxu Fan1,2, Yun Wang1,2 , Peihua Qu1,2, Shinian Fu1,2,3 1 Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, China 2 Dongguan Neutron Science Center, Dongguan 523803, China 3 University of Chinese Academy of Sciences, Beijing, 100049, China Abstract The China Spallation Neutron Source (CSNS) Drift tube linac (DTL) accelerates Hbeam from 3 to 80MeV with 4 independent tanks. The 80MeV beam acceleration was achieved in January 2018. The linac is a key to the reliability of the whole CSNS facility since all the beams stop when these upstream facilities fail. Many efforts have been made for DTL reliable operation. This paper presents the operation experience learned in DTL commissioning.

CSNS front end is currently under running, which consists of a H⁻ penning ion source(IS), a low energy beam transport(LEBT), a radio frequency quadrupole (RFQ) and a medium energy beam transport(MEBT). CSNS ion source is a type of Penning surface plasma source, similar to ISIS ion source. Cesium is used to enhance the H⁻ ion production efficiency. The ion source is running with duty factor of 1.25%(25Hz and 500us). Normally, 40mA H⁻ beam from ion source with 50keV can be delivered into LEBT. Three solenoids and two direction magnets are employed to transport and match the beam from the ion source into the RFQ. The pre-chopper is installed at the end of LEBT. The chopper mainly works at 3.8-4.2 kV and 1 MHz rate, which is about the RF frequency of the ring at injection. The rise time is less than 10ns，which fulfills the requirement of ring injection. For the RFQ, it is a 324MHz 4-vane type with a output energy of 3.0MeV and the length of 3.62m. The input cavity power is about 400kW. During commissioning, 16mA H⁻ beam can be obtained at the exit of RFQ, and the RFQ transmission rate is up to 94%.

China Spallation Neutron Source (CSNS) accelerator complex consists of a front end, an 80MeV DTL linac, and a 1.6GeV Rapid Cycling Synchrotron (RCS).It is designed with a beam power of 100kW in the first phase and reserves upgrade capability to 500kW in the second phase. It has completed initial beam commissioning and has started user operation in 2018. And meanwhile the beam power is quickly going up from the initially above 10kW to 50kW during the user operation, and we can foresee that the designed beam power of 100 kW can be reached in the next year. This paper gives the recent status of beam commissioning, beam power ramping, user operation, as well as future upgrade plan to increase the beam power up to 500 kW.

Multipacting is a phenomenon in which electrons grow sharply under certain conditions in a RF structure. It may lead to the breakdown or even damage to the equipment. Therefore, it is very important to calculate the Multipacting range in the RF equipment design. Since the phenomenon is too complicated to use the formula to fully predict it, numerical simulation is employed. There are many computer codes (such as Track3P, MultiPac, CST PS, etc.) used to simulate the phenomenon, but most of them are not commercial. In this paper, theories used in coaxial line for predicting multipacting are introduced; the CST PS is chosen to simulate the multipacting of coaxial coupler for BNCT DTL; finally, methods of suppressing multipacting are discussed.

The China Spallation Neutron Source(CSNS) accelerator systems is designed to deliver a 1.6GeV, 100kW proton beam to a solid metal target for neutron scattering research. The accelerator consists of a front end, an 80MeV DTL linac, and a 1.6GeV Rapid Cycling Syn-chrotron (RCS). In August 2017 the first 1.6GeV proton beam hit on the tungsten target and production neutrons were monitored. This paper will report the major steps and results of the machine commissioning and beam commissioning of the CSNS front end and linac. In the first section, a brief introduction of the CSNS accelerator design and present status will be presented. Then, we will share our commissioning experience in the front end and the DTL linac in the following sections.

The China Spallation Neutron Source(CSNS) accelera-tor systems is designed to deliver a 1.6GeV, 100kW pro-ton beam to a solid metal target for neutron scattering research. It consists of a 50keV H⁻ Ion Source, a 3MeV Radio Frequency Quadrupole (RFQ), an 80MeV Drift Tube Linac (DTL), and a 1.6GeV Rapid-cycling Synchro-tron (RCS). The DTL consists of four tanks. In 2017, three of four tanks have been commissioned successfully, and beam has been accelerated to 61MeV with nearly 100% transmission. However, in July 2017, one quadrupole contained in the drift tube was found fault, the beam transmission decreased to 80%. A new lattice has been designed and the 100% transmission has recovered. In January 2018, the last tank of the DTL has been commissioned and accelerated the H⁻ beam to the design energy of 80MeV for the first time. The commissioning progress and the measurement results before and after lattice adjustment will be presented.