2018 Fiscal Year Research-status Report
Study of primary knock-on atoms from high-energy proton bombardment
| Project/Area Number |
17K14918
|
|---|
| Research Institution | Japan Atomic Energy Agency |
|---|
Principal Investigator |
蔡 碧恩 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 原子力科学研究所 原子力基礎工学研究センター, 研究員 (50781671)
|
|---|
| Project Period (FY) |
2017-04-01 – 2020-03-31
|
| Keywords | PKA / gas ionization chamber / dE-E / particle identification |
|---|
| Outline of Annual Research Achievements |
Experimental data of primary knock-on atoms (PKAs) produced from proton-induced nuclear reactions are needed for the radiation damage assessment and validating nuclear physics models for various accelerator applications. This study proposed a new measurement system consisting of two ultra-fast timing detectors and one customized dE-E gas ionization chamber (GIC) to provide the missing experimental data.
This study in the second year was focused on establishing the dE-E GIC, which includes its gas flow system. The detector operation conditions, such as its applied high voltages, mass flow rate, and operation gas pressures in correspondence to its window material and thickness, were tested and optimized at the JAEA Tandem Facility by using an Am-241 alpha source. The dE-E GIC was further tested for its particle identification performance with the use of a 70-MeV proton beam bombarding a 900-nm thick C target at CYRIC, Tohoku University.
The preliminary experimental results show that the dE-E GIC is able to separate He, Li, Be, B, C elements over < 1 MeV/nucleon, whose discrimination thresholds depend on the operation gas pressure and the atomic weight of the particles. However, the energy resolution of the detector can still be further improved for better particle identification performance by (1) using a thinner detector window and a thinner target, (2) improving the back-end electronics design, and (3) decreasing the electronic noises in the following fiscal year.
|
| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The detector development of the new measurement system was expected to finish by the end of the second fiscal year. The part for the dE-E gas ionization chamber along with its gas flow system and back-end electronics has been done as scheduled. The experimental data measured by GIC at CYRIC with its 70-MeV proton beam is still in the progress for data analysis, but the preliminary results look promising and have been presented at a domestic conference. In the following fiscal year, the GIC is planned to be further improved for better energy resolutions and hence better particle identification capability.
As to the part for the ultra-fast timing detectors, the prototype made in the first fiscal year had been further modified intending to approve the coincidence rate of two detectors. However, the test result was still not satisfactory, so the improvement is still ongoing.
|
| Strategy for Future Research Activity |
The data analysis of the experimental data acquired in the previous fiscal year will be done in this fiscal year. More in-house detector tests for the modified timing detector assembly and the dE-E gas ionization chamber will be conducted at the JAEA Tandem Facility with an Am-241 calibration alpha source. Then more measurements of the energy-, mass-, and angular-dependent PKA production cross sections with different target materials bombarded by 70-MeV protons are planned to be performed during the No. 133 CYRIC machine time.
The outcome of this study will be summarized and presented at an international conference.
|
| Causes of Carryover |
1. The purchase of new isobutane gas was abruptly cancelled due to the fact that the opening of tender was abortive in FY2018, so it will be postponed to this year.
2. Part of the budget was originally planned for purchasing different target materials for the experiments if the detectors development and tests were performed as we expected. However, the schedule is slightly delayed, so the purchase is delayed to FY2019.
3. Part of the deferred budget is also planned to be used on the detector modification and improvement. The originally scheduled budget will be spent on the travel expenses for presenting at an international conference.
|
