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Multi Bunch Beam Generation using a Mode Separated Photocathode RF Gun
https://ir.soken.ac.jp/records/2163
https://ir.soken.ac.jp/records/2163ae62f643-a62a-41d5-ad88-837f1884f374
| 名前 / ファイル | ライセンス | アクション |
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要旨・審査要旨 (248.6 kB)
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本文 (8.7 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
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| 公開日 | 2011-06-03 | |||||
| タイトル | ||||||
| タイトル | Multi Bunch Beam Generation using a Mode Separated Photocathode RF Gun | |||||
| タイトル | ||||||
| タイトル | Multi Bunch Beam Generation using a Mode Separated Photocathode RF Gun | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
DESHPANDE, ABHAY PRALHAD
× DESHPANDE, ABHAY PRALHAD |
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| フリガナ |
ディシュパンデ, アブヘイ パラールハド
× ディシュパンデ, アブヘイ パラールハド |
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| 著者 |
DESHPANDE, ABHAY PRALHAD
× DESHPANDE, ABHAY PRALHAD |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第1378号 | |||||
| 研究科 | ||||||
| 値 | 高エネルギー加速器科学研究科 | |||||
| 専攻 | ||||||
| 値 | 12 加速器科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2010-09-30 | |||||
| 学位授与年度 | ||||||
| 値 | 2010 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | The Accelerator Test Facility (ATF) at KEK designed the RF gun with Cs<small>2</small>Te photo-cathode for the Laser Undulator Compact X-ray source (LUCX) and ATF linac. The first gun made at KEK was based on Brookhaven National Laboratory (BNL) gun design. Subsequently many improvements were made and an improved gun design was established. Based on the improved gun, eight guns were made by KEK and installed at various institutions in Japan. The expertise thus evolved at KEK for the RF guns from 2002 to 2008. The next request was now to further reduce the beam emittance and make beam energy spread stable over wider range in laser injection phase. It was also essential to increase the charge per bunch and number of bunches per train for increasing the x-ray flux from the LUCX. Around 2005, the Linac Coherent Light Source (LCLS) group at Stanford Linear Accelerator Center (SLAC) suggested that by increasing mode separation, more stability over injection phase variations could be achieved. LCLS group changed their own design to increase the mode separation up to 15 MHz. Following this approach, we decided to increase the mode separation. An advantage in our case is that we also made a new profile for the new gun to achieve high Q (unloaded qualityfactor) and high shunt impedance. In this thesis we discuss the evolution of the design of the new gun structure and the procedure which we established to fabricate and process the RF gun. We show the experimental results of measurements and details of the tuning process to achieve the desired frequency at π mode of 2856 MHz with mode separation of 8.6 MHz maintaining the field balance at 1.0. The new gun has higher Q, higher shunt impedance and large mode separation than any gun made at KEK as well as the LCLS gun or the BNL gun. The observed dark currents are also less than earlier gun. Our experience with new large mode separation gun coupled with 130 MV/m fields and Cs<small>2</small>Te cathode is a very essential experience for making Cs<small>2</small>Te a well acceptable material for photo cathode guns. Beam dynamics simulations were done to estimate the trends of parameter variations. At present, PARMELA, ASTRA, GPT are the three most widely used codes for beam dynamics simulations of the RF guns. We decided to use ASTRA for the beam dynamics simulations of new RF gun mainly because it is much simple to use, free-of-charge and has been bench marked using many new RF gun. The main focus of beam quality measurement was to compare the parameters for new RF gun with those for the old RF gun, where ever possible. The dependence of emittance was measured as a function of solenoid field, laser injection phase, laser spot size and charge. These measurements played crucial role to fix the optimum operational parameters for the RF gun. We measured the emittance value of 1.89 π-mm-mrad at 1nC charge. Efforts are on-going to check system alignment to push this emittance down to 1.0 π-mm-mrad. Variation in energy spread over the injection phase was also a parameter that we focused upon. The larger mode separation helps to maintain low energy spread over wider phase range. This was observed after careful experimentation. The thermal emittance issue is discussed in the thesis. We try to estimate the thermal emittance using an indirect method. Direct measurement was not possible due to various limitations of the present setup. We propose to measure the thermal emittance by direct method in near future and we are making changes in our setup accordingly. We conclude that the three step model as it exists today is not sufficient to explain the measured value of thermal emittance for semiconductor photocathode. Hence detailed study will be helpful to understand the complexities of factors involved, which affect the thermal emittance. Another striking feature of the work done at LUCX is to establish the methods for generation of long multi bunch beam. We succeeded in generating 100-bunches with 0.5 nC per bunch at 40 MeV with peak to peak energy difference less than 0.7%. In other experiment we generate low energy beam of 5 MeV. In this case we succeed to generate 300-bunches with 0.55 nC per bunch with peak to peak energy difference less than 0.85%. These results are very important results for our efforts to make 8000-bunches per train as a first step. We hope to achieve this goal by the end of this year (2010). At LUCX we are trying to establish the generation of very long pulse trains and we wish to achieve 8000 bunches per train. The future of compact x-ray sources will depend on how long trains with high charge and low energy dfference. It will be possible in few years to get very high flux x-ray from such sources. The present thesis is focused on new design of large mode separation gun, fabrication and tuning of the gun. Then tuning this gun to get a low emittance beam and there after generate 300-bunches per train is described. |
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| 値 | 有 | |||||
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| 内容記述タイプ | Other | |||||
| 内容記述 | application/pdf | |||||
