Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma

Wakefield excitation by long sequence of short Gaussian bunches of relativistic electrons and electron bunch acceleration in excited wakefield is numerically simulated for the parameters of the experiments. It is shown that at change of the system parameters and shaping laws of sequence of bunches o...

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Datum:2015
Hauptverfasser: Levchuk, I.P., Maslov, V.I., Onishchenko, I.N.
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Veröffentlicht: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2015
Schriftenreihe:Вопросы атомной науки и техники
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spelling irk-123456789-1123612017-01-21T03:02:42Z Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma Levchuk, I.P. Maslov, V.I. Onishchenko, I.N. Новые и нестандартные ускорительные технологии Wakefield excitation by long sequence of short Gaussian bunches of relativistic electrons and electron bunch acceleration in excited wakefield is numerically simulated for the parameters of the experiments. It is shown that at change of the system parameters and shaping laws of sequence of bunches of relativistic electrons in the intervals of finite width the transformation ratio remains large. Числовим моделюванням досліджується для параметрів експериментів збудження кільватерного поля до-вгою послідовністю коротких гауссівських згустків релятивістських електронів і прискорення електронних згустків з малим зарядом у збудженому полі. Показано, що при зміні параметрів системи і законів профілювання послідовності згустків релятивістських електронів в інтервалах кінцевої ширини коефіцієнт трансформації залишається значним. Численным моделированием исследуется для параметров экспериментов возбуждение кильватерного по-ля длинной последовательностью коротких гауссовских сгустков релятивистских электронов и ускорение электронных сгустков с малым зарядом в возбужденном поле. Показано, что при изменении параметров системы и законов профилирования последовательности сгустков релятивистских электронов в интервалах конечной ширины коэффициент трансформации остается большим. 2015 Article Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma / I.P. Levchuk, V.I. Maslov, I.N. Onishchenko // Вопросы атомной науки и техники. — 2015. — № 6. — С. 37-41. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 29.17.+w; 41.75.Lx; http://dspace.nbuv.gov.ua/handle/123456789/112361 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Новые и нестандартные ускорительные технологии
Новые и нестандартные ускорительные технологии
spellingShingle Новые и нестандартные ускорительные технологии
Новые и нестандартные ускорительные технологии
Levchuk, I.P.
Maslov, V.I.
Onishchenko, I.N.
Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
Вопросы атомной науки и техники
description Wakefield excitation by long sequence of short Gaussian bunches of relativistic electrons and electron bunch acceleration in excited wakefield is numerically simulated for the parameters of the experiments. It is shown that at change of the system parameters and shaping laws of sequence of bunches of relativistic electrons in the intervals of finite width the transformation ratio remains large.
format Article
author Levchuk, I.P.
Maslov, V.I.
Onishchenko, I.N.
author_facet Levchuk, I.P.
Maslov, V.I.
Onishchenko, I.N.
author_sort Levchuk, I.P.
title Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
title_short Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
title_full Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
title_fullStr Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
title_full_unstemmed Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
title_sort transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
publishDate 2015
topic_facet Новые и нестандартные ускорительные технологии
url http://dspace.nbuv.gov.ua/handle/123456789/112361
citation_txt Transformation ratio at wakefield excitation by linearly shaped sequence of short relativistic electron bunches in plasma / I.P. Levchuk, V.I. Maslov, I.N. Onishchenko // Вопросы атомной науки и техники. — 2015. — № 6. — С. 37-41. — Бібліогр.: 8 назв. — англ.
series Вопросы атомной науки и техники
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AT maslovvi transformationratioatwakefieldexcitationbylinearlyshapedsequenceofshortrelativisticelectronbunchesinplasma
AT onishchenkoin transformationratioatwakefieldexcitationbylinearlyshapedsequenceofshortrelativisticelectronbunchesinplasma
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fulltext ISSN 1562-6016. ВАНТ. 2015. №6(100) 37 TRANSFORMATION RATIO AT WAKEFIELD EXCITATION BY LINEARLY SHAPED SEQUENCE OF SHORT RELATIVISTIC ELECTRON BUNCHES IN PLASMA I.P. Levchuk, V.I. Maslov, I.N. Onishchenko National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine E-mail: vmaslov@kipt.kharkov.ua Wakefield excitation by long sequence of short Gaussian bunches of relativistic electrons and electron bunch ac- celeration in excited wakefield is numerically simulated for the parameters of the experiments. It is shown that at change of the system parameters and shaping laws of sequence of bunches of relativistic electrons in the intervals of finite width the transformation ratio remains large. PACS: 29.17.+w; 41.75.Lx; INTRODUCTION Transformation ratio is the important value in the wakefield method of charged particle acceleration (see, for example, [1 - 5]). It determines to what energy the electrons can be accelerated by sequence of electron bunches with fixed energy. The transformation ratio, determined as the ratio TE=E2/E1 of wakefield E2, which is excited in plasma by sequence of electron bunches to the field E1, in which the electron bunch is decelerated, is considered. The excitation of wakefield by long se- quence of short Gaussian bunches of relativistic elec- trons is investigated by numerical simulation, using the code lcode [6], for the parameters of the experiments [7, 8]. The distance between the bunches, equal to wavelength plus the bunch width at half-maximum, and the distance between bunches, equal to one and a half of the wavelength, are selected. It is shown that not only in these cases, but also at varying of the parameters within a certain range the transformation ratio increases with the number of bunches. 1. ANALYTICAL INVESTIGATION OF WAKEFIELD EXCITATION IN PLASMA WITH LARGE TRANSFORMATION RATIO BY SEQUENCE OF BUNCHES WITH LINEAR GROWTH OF CHARGE First we analytically compare the wakefield, excited by resonance (ωm=ωpe, ωm is the repetition frequency of bunches, ωpe is the electron plasma frequency) sequence of rectangular (uniform) bunches with the ratio of the successive charges, equal to 1:3:5: … with 1.5ωm=ωpe. At using of shaped bunches through 1.5λ the decel- erating field is equal to Esl=E1/2, and the accelerating field is equal to Eac=NE1. N is the number of bunches. I.e. after 2nd bunch Eac=2E1, and after 3rd bunch Eac=3E1. In the case of resonant shaped bunches through λ the decelerating wakefield is approximately equal to the accelerating wakefield and accelerating wakefield after 2nd bunch is equal to Eac=4E1, after 3rd bunch it is equal to Eac=9E1, i.e. it should be Eac=N2E1. Indeed WN-WN-1 = ηεN, εN = 2πenbcENc/ωp, ENc = EN-1+βδEN β≈1/2. Then after 1st bunch one can derive ε1 = πenb1cδE1/ωp, W1 = ηε1, δE1 = E1, W1 = E1 2/4π E1 2/4π = ηπenb1cE1/ωp, E1 = (2π)2ηenb1c/ωp. After 2nd bunch one can derive W2-W1 = ηε2, ε2 = 2πe3nb1cENc/ωp, ENc = E1+δE2/2. (E1+δE2)2/4π-E1 2/4π = = δE2(E1+δE2/2)/2π = η6πenb1c(E1+δE2/2)/ωp δE2 = 3η(2π)2enb1c/ωp = 3E1. Hence after 2nd bunch E2 = E1+δE2 = 4E1. After N-th bunch WN-WN-1 = ηεN, εN = 2πenbcENc/ωp, ENc = EN-1+δEN/2. EN 2/4π-EN-1 2/4π = (EN-1+δEN)2/4π-EN-1 2/4π = = δEN(E1+δEN/2)/2π = η2πe(2N-1)nb1c(EN-1+δEN/2)/ωp, δEN = η(2π)2e(2N-1)nb1c/ωp = (2N-1)E1. Then E3 = E2+δE3 = 4E1+5E1 = 9E1. EN = EN-1+δEN∼1+3+…+(2N-1) 1+3+...+(2N-1) = 1+2+...+2N-2(1+2+...+N). Because 1+2+...+N = N(N+1)/2, we have 1+3+…+(2N-1) = 2N(2N+1)/2-2N(N+1)/2 = N2. EN = N2E1. Then after 300 bunches the accelerating fields in resonant shaped case through λ EN (res) and in shaped case through 1.5λ EN (sh) are different in EN (res)/EN (sh)=N2E1/NE1=N=300 times. In the case of shaped bunches through 1.5λ the de- celerating wakefield is in 300 times smaller than the accelerating wakefield and in (300)2≈105 times smaller than the wakefield in resonant case. 2. NUMERICAL SIMULATION OF WAKEFIELD EXCITATION IN PLASMA WITH LARGE TRANSFORMATION RATIO BY SEQUENCE OF BUNCHES WITH LINEAR GROWTH OF CHARGE Numerical simulation has been performed using 2d3v- code lcode [6]. Parameters: nres=1011cm-3 is the resonant plasma density which corresponds to ratio ωpe=ωm=2π·2.8·109, relativistic factor of bunches equals γb=5, have been selected for numerical simulation. ωm is the repetition frequency of bunches, ωpe= (4πnrese2/me)1/2 is the electron plasma frequency. The density of bunches 8 3 bn 6 10 ñm−= × is distributed in the transverse direction approximately according to Gaussian distribution, ISSN 1562-6016. ВАНТ. 2015. №6(100) 38 r 0.5cmσ = , 10.55cmλ = is the wavelength, ξ=Vbt-z, Vb is the velocity of bunches. Time is normalized on ωpe -1, dis- tance – on c/ωpe, density − on nres, current Ib – on Icr=πmc3/4e, fields – on (4πnresc2me)1/2. We show that in the case of often used shaped bunches-uniform-cylinders with the ratio of charges, equal to 1:3:5:... and with the distance between bunches, equal to one and half of the wavelength δξ=1.5λ, with a width of bunches, equal to ξb=λ/2, at of plasma wake- field excitation the problem of the formation of the ac- celerated bunch is solved easily. In this case, the last bunch, if its charge is small in comparison with the charge of previous bunch, becomes accelerated bunch (Figs. 1-3). Fig. 1. Current of bunches with ξb=λ/2, δξ=1.5λ, q1:q2:q3: … =1:3:5: … at linear growth and sharp decrease at back front Fig. 2. Longitudinal distribution of density nb of sequence of bunches and of longitudinal wakefield Ez in the case of sequence of bunches with the ratio of the successive charges, equal to 1:3:5:…, at ξb=λ/2, Ib=0.2·10-3 The wakefield excitation by sequence of N bunches with the ratio of the charges of the successive bunches, equal to 1:3:5: ..., the distance between bunches, equal to the sum of the excited wavelength λ and bunch width at half maximum ξb is considered. One can see (Fig. 4), that bunches on part of the sequence, on which the charges of bunches increases, get into small decelerating wakefield. Thus the large transformation ratio achieves, which can be determined as the ratio of the maximum accelerating wakefield Ema to the maximum decelerating wakefield Emd in the area of bunch TR=Ema/Emd. Also one can see that on the back front of the sequence, where the charges of bunches decrease, the bunches automatically get into large accelerating wakefield. Fig. 3. Perturbation of longitudinal momenta δpz of bunches When bunches are formed due to trapping of elec- trons with linearly increasing charge density by electric field on each successive identical time interval and due to their bunching and when on half periods of time elec- trons are lost, then the ratio of charges of consecutive bunches is equal to 1:5:9: ... If the distance between the bunches is equal to the sum of the excited wavelength and of the width of the bunch at half-maximum, then (Fig. 5) the amplitude of the beatings of decelerating wakefield, in which bunches get, is more. However, the transformation ratio remains large. Again at the back front of the sequence, in which the charges of the bunches de- crease, bunches get into large accelerating field. In the case of a sequence of 45 bunches with the ra- tio of charges of the successive bunches, equal 1:5:9: ..., excited wakefield has the shape, shown in Fig. 6. In the case of a sequence of 100 bunches with the ratio of charges of the successive bunches, equal 1:3:5: ..., excit- ed wakefield has the shape, shown in Fig. 7. If the ratio of the charges of successive bunches is equal to 1:2:3: ... [2] and the distance between bunches is equal to the sum of excited wavelength and of width of the bunch at half-maximum, and the charge of bunch- es distributed in the longitudinal direction according to the Gaussian distribution, the excited wakefield has the shape, shown in Fig. 8. One can see that at the back front of the sequence, in which the charges of the bunches decrease, bunches get automatically into large accelerating wakefield. If the distance between the bunches, the charge of which is distributed in the longitudinal direction accord- ing to Gauss distribution, is equal to one and half of the wavelength, the length of the bunch at the base equals to the wavelength and the charge ratio of successive bunches is equal to 1:3:5: ... the excited wakefield has the shape, shown in Fig. 9. One can see that decelerating wakefield is small and approximately the same for the majority of the bunch electrons. The bunches are in fairly homogeneous close focusing wakefields (see Fig. 9) due to the fact that the bunches get into the dips of the plas- ma electron density (Fig. 10). If the distance between the bunches, the charge of which is distributed in the longitudinal direction accord- ing to Gauss distribution, is equal to two and half of the wavelength, the length of the bunch at the base equals to the wavelength and the charge ratio of successive bunches is equal to 1:3:5: ... the excited wakefield has the shape, shown in Fig. 11. One can see that decelerat- ing wakefield is also small and approximately the same for the majority of the bunch electrons. In the case of linear shaping of charges of bunch se- quence along the sequence as well as along each bunch with use of bunch-precursor the large transformation ratio is achieved (Fig. 12) TR≈2πNξb/λ. One can see that the wakefield amplitude and the transformation ratio increase with increasing of number of bunches, exciting wakefield. Now we consider the range of change parameters in which the transformation ratio remains large. Numerical simulation shows that TR and the accelerating wakefield are large in the case of parameter changes 2πV0/ωm=λ+ξb in range 2πV0/ωm=λ+ξb±ξb/2. However, in these cases the decelerating wakefield and their spa- tial distributions are different (see Figs. 4, 13, 14). ISSN 1562-6016. ВАНТ. 2015. №6(100) 39 Fig. 4. Longitudinal distribution of density nb of sequence of bunches and of longitudinal wakefield Ez in the case of sequence of bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … with the distance between the Gaussian bunches, equal to the sum of excited wavelength and of width of the bunch at half-maximum at ξb=λ/6, Ib=0.7·10-3 Fig. 5. Longitudinal distribution of density nb of sequence of bunches and of longitudinal wakefield Ez in the case of sequence of 17 bunches with the ratio of charges of the successive bunches, equal to 1:5:9: … with the distance between the the Gaussian bunches, equal to the sum of excited wavelength and of width of the bunch at half-maximum at ξb=λ/6, Ib=0.7·10-3 Fig. 6. Longitudinal distribution of density nb of sequence of bunches and of longitudinal wakefield Ez in the case of sequence of 45 bunches with the ratio of charges of the successive bunches, equal to 1:5:9: … with the distance between the Gaussian bunches, equal to the sum of excited wavelength and of width of the bunch at half-maximum at ξb=λ/6, Ib=0.23·10-3 Fig. 7. Longitudinal distribution of density nb of sequence of the Gaussian bunches and of longitudinal wakefield Ez in the case of sequence of 100 bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … at ξb=λ/6, Ib=0.18·10-3 ISSN 1562-6016. ВАНТ. 2015. №6(100) 40 Fig. 8. Longitudinal distribution of density nb of sequence of bunches and of longitudinal wakefield Ez in the case of se- quence of bunches with the ratio of charges of the successive bunches, equal to 1:2:3: … with the distance between the bunches, equal to the sum of excited wavelength and of width of the bunch at half-maximum at ξb=λ/6, Ib=0.7·10-3 Fig. 9. Longitudinal distribution of density nb of sequence of bunches, of longitudinal wakefield Ez and of radial wake force Fr in the case of sequence of the Gaussian bunches with the ratio of charges of the successive bunch- es, equal to 1:3:5: … with the distance between the bunches, equal to one and half of the wavelength, the length of the bunch at the base equals to the wavelength at ξb=λ/2, Ib=0.7·10-3 Fig. 10. Longitudinal distribution of density nb of sequence of bunches and of density of plasma electrons ne in the case of sequence of bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … with the distance between the bunches, equal to one and half of the wavelength, the length of the bunch at the base equals to the wavelength Fig. 11. Longitudinal distribution of density nb of sequence of the Gaussian bunches and of longitudinal wakefield Ez in the case of sequence of bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … with the distance between the bunches, equal to two and half of the wavelength, the length of the bunch at the base equals to the wavelength at ξb=λ/2, Ib=0.7·10-3 Fig. 12. Longitudinal distribution of density nb of sequence of short bunches and of longitudinal wakefield Ez in the case of linear shaping of charges of bunch sequence along the sequence as well as along each bunch with use of bunch-precursor at ξb=λ/20, Ib=1.0·10-3 ISSN 1562-6016. ВАНТ. 2015. №6(100) 41 Fig. 13. Longitudinal distribution of density nb of sequence of the Gaussian bunches and of longitudi- nal wakefield Ez in the case of sequence of bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … with the distance between the bunches, equalλ+ξb+ξb/2 at ξb=λ/6, Ib=0.7·10-3 Fig. 14. Longitudinal distribution of density nb of sequence of the Gaussian bunches and of longitudi- nal wakefield Ez in the case of sequence of bunches with the ratio of charges of the successive bunches, equal to 1:3:5: … with the distance between the bunches, equal λ+ξb-ξb/2 at ξb=λ/6, Ib=0.7·10-3 CONCLUSIONS The transformation ratio has been investigated by the numerical simulation at wakefield excitation in plasma by sequence of Gaussian short relativistic electron bunches with linearly increasing charges. It has been shown that the transformation ratio increases with the increasing of number of bunches when the distance be- tween bunches is equal to the sum of excited wavelength and of width of the bunch at half-maximum and when the distance between the bunches is equal to the one and half of the wavelength. REFERENCES 1. E. Kallos, T. Katsouleas, P. Muggli, et al. Plasma wakefield acceleration utilizing multiple electron bunches // Proc. PAC07, Albuquerque, New Mexico, USA, 2007, p. 3070-3072. 2. V.A. Balakirev, I.N. Onishchenko, G.V. Sotnikov, Ya.B. Fainberg. Charged particle acceleration in plasma by wakefield of shaped train of relativistic electron bunches // Plasma Phys. 1996, v. 22, № 2, p. 157-164. 3. K.V. Lotov, V.I. Maslov, I.N. Onishchenko, I.P. Yarovaya. Transformation Ratio at Interaction of Long Sequence of Electron Bunches with Plasma // Problems of Atomic Science and Technology. Series “Nuclear Physics Investigations”. 2011, № 3, p. 87-91. 4. K. Nakajima, Plasma wake-field accelerator driven by a train of multiple bunches // Particle Accelera- tors. 1990, v. 32, p. 209-214. 5. E.M. Laziev, E.V. Tsakanov, S. Vahanyan, // Elec- tromagnetic wave generation with high transfor- mation ratio by intense charged particle bunches // EPAC IEEE. 1988, p. 523. 6. K.V. Lotov. Simulation of ultrarelativistic beam dy- namics in plasma wake-field accelerator // Phys. Plasmas. 1998, v. 5, № 3, p. 785-791. 7. А.К. Berezin, Ya.B. Fainberg, V.A. Kiselev, et al. Wakefield excitation in plasma by relativistic elec- tron beam, consisting regular chain of short bunches // Plasma Physics. 1994, v. 20, № 7-8, p. 663-670. 8. V.A. Kiselev, A.F. Linnik, V.I. Mirny, et al. Experi- ments on resonator concept of plasma wakefield ac- celerator driven by a train of relativistic electron bunches // Problems of Atomic Science and Technolo- gy. Series “Plasma Physics”. 2008. № 6, p. 135-137. Article received 20.10.2015 КОЭФФИЦИЕНТ ТРАНСФОРМАЦИИ ПРИ ВОЗБУЖДЕНИИ КИЛЬВАТЕРНОГО ПОЛЯ ЛИНЕЙНО ПРОФИЛИРОВАННОЙ ПОСЛЕДОВАТЕЛЬНОСТЬЮ КОРОТКИХ РЕЛЯТИВИСТСКИХ ЭЛЕКТРОННЫХ СГУСТКОВ В ПЛАЗМЕ И.П. Левчук, В.И. Маслов, И.Н. Онищенко Численным моделированием исследуется для параметров экспериментов возбуждение кильватерного по- ля длинной последовательностью коротких гауссовских сгустков релятивистских электронов и ускорение электронных сгустков с малым зарядом в возбужденном поле. Показано, что при изменении параметров си- стемы и законов профилирования последовательности сгустков релятивистских электронов в интервалах конечной ширины коэффициент трансформации остается большим. КОЕФІЦІЄНТ ТРАНСФОРМАЦІЇ ПРИ ЗБУДЖЕННІ КІЛЬВАТЕРНОГО ПОЛЯ ЛІНІЙНО ПРОФІЛЬОВАНОЮ ПОСЛІДОВНІСТЮ КОРОТКИХ РЕЛЯТИВІСТСЬКИХ ЕЛЕКТРОННИХ ЗГУСТКІВ У ПЛАЗМІ І.П. Левчук, В.І. Маслов, І.М. Оніщенко Числовим моделюванням досліджується для параметрів експериментів збудження кільватерного поля до- вгою послідовністю коротких гауссівських згустків релятивістських електронів і прискорення електронних згустків з малим зарядом у збудженому полі. Показано, що при зміні параметрів системи і законів профілю- вання послідовності згустків релятивістських електронів в інтервалах кінцевої ширини коефіцієнт трансфор- мації залишається значним. INTRODUCTION 1. ANALYTICAL INVESTIGATION OF WAKEFIELD EXCITATION IN PLASMA WITH LARGE TRANSFORMATION RATIO BY SEQUENCE OF BUNCHES WITH LINEAR GROWTH OF CHARGE 2. NUMERICAL SIMULATION OF WAKEFIELD EXCITATION IN PLASMA WITH LARGE TRANSFORMATION RATIO BY SEQUENCE OF BUNCHES WITH LINEAR GROWTH OF CHARGE