RF-cavity for the X-ray generator NESTOR

In the Kharkov Institute of Physics and Technology 225 MeV electron storage ring NESTOR is under development. The paper describes the design and parameters of a 700 MHz cavity that has been fabricated at BINP for the NESTOR RF-system. Now the low-power and vacuum tests of the cavity are under way at...

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Опубліковано в: :Вопросы атомной науки и техники
Дата:2007
Автори: Androsov, V.P., Chernov, K.N., Gvozd, A.M., Karnaukhov, I.M., Ostreyko, G.N., Sedlyarov, I.K., Telegin, Y.N.
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Опубліковано: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2007
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Цитувати:RF-cavity for the X-ray generator NESTOR / V.P. Androsov, K.N. Chernov, A.M. Gvozd, I.M. Karnaukhov, G.N. Ostreyko, I.K. Sedlyarov, Y.N. Telegin // Вопросы атомной науки и техники. — 2007. — № 5. — С. 151-155. — Бібліогр.: 9 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-110565
record_format dspace
spelling Androsov, V.P.
Chernov, K.N.
Gvozd, A.M.
Karnaukhov, I.M.
Ostreyko, G.N.
Sedlyarov, I.K.
Telegin, Y.N.
2017-01-04T19:37:20Z
2017-01-04T19:37:20Z
2007
RF-cavity for the X-ray generator NESTOR / V.P. Androsov, K.N. Chernov, A.M. Gvozd, I.M. Karnaukhov, G.N. Ostreyko, I.K. Sedlyarov, Y.N. Telegin // Вопросы атомной науки и техники. — 2007. — № 5. — С. 151-155. — Бібліогр.: 9 назв. — англ.
1562-6016
PACS: 29.20.Dh, 29.27.Bd
https://nasplib.isofts.kiev.ua/handle/123456789/110565
In the Kharkov Institute of Physics and Technology 225 MeV electron storage ring NESTOR is under development. The paper describes the design and parameters of a 700 MHz cavity that has been fabricated at BINP for the NESTOR RF-system. Now the low-power and vacuum tests of the cavity are under way at BINP. We present here the results of 3D simulations of the cavity with ANSYS code. The problem of multibunch instabilities in NESTOR is also discussed.
В ННЦ ХФТІ споруджується електронне накопичувальне кільце НЕСТОР на енергію 225 МеВ. У роботі описується конструкція та приводяться параметри резонатора на 700 МГц, виготовленого в ІЯФ СВ РАН ім. Будкера для ВЧ-системи накопичувача. У дійсний час резонатор проходить вакуумні випробування та радіотехнічні вимірювання в ІЯФ. У роботі також приводяться результати 3D моделювання резонатору за допомогою програми ANSYS. Обговорюється також проблема багатозгусткових нестійкостей у накопичувачі НЕСТОР.
В ННЦ ХФТИ сооружается электронное накопительное кольцо НЕСТОР на энергию 225 МэВ. В работе описывается конструкция и приводятся параметры резонатора на 700 МГц, изготовленного в ИЯФ СО РАН им. Будкера для ВЧ-системы накопителя. В настоящее время резонатор проходит вакуумные испытания и радиотехнические измерения в ИЯФ. В работе также приводятся результаты 3D моделирования резонатора с помошью программы ANSYS. Обсуждается также проблема много- сгустковых неустойчивостей в накопителе НЕСТОР.
en
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
Вопросы атомной науки и техники
Теория и техника ускорения частиц
RF-cavity for the X-ray generator NESTOR
ВЧ-резонатор для генератора рентгенівського випромінювання НЕСТОР
ВЧ-резонатор для генератора рентгеновского излучения НЕСТОР
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title RF-cavity for the X-ray generator NESTOR
spellingShingle RF-cavity for the X-ray generator NESTOR
Androsov, V.P.
Chernov, K.N.
Gvozd, A.M.
Karnaukhov, I.M.
Ostreyko, G.N.
Sedlyarov, I.K.
Telegin, Y.N.
Теория и техника ускорения частиц
title_short RF-cavity for the X-ray generator NESTOR
title_full RF-cavity for the X-ray generator NESTOR
title_fullStr RF-cavity for the X-ray generator NESTOR
title_full_unstemmed RF-cavity for the X-ray generator NESTOR
title_sort rf-cavity for the x-ray generator nestor
author Androsov, V.P.
Chernov, K.N.
Gvozd, A.M.
Karnaukhov, I.M.
Ostreyko, G.N.
Sedlyarov, I.K.
Telegin, Y.N.
author_facet Androsov, V.P.
Chernov, K.N.
Gvozd, A.M.
Karnaukhov, I.M.
Ostreyko, G.N.
Sedlyarov, I.K.
Telegin, Y.N.
topic Теория и техника ускорения частиц
topic_facet Теория и техника ускорения частиц
publishDate 2007
language English
container_title Вопросы атомной науки и техники
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
format Article
title_alt ВЧ-резонатор для генератора рентгенівського випромінювання НЕСТОР
ВЧ-резонатор для генератора рентгеновского излучения НЕСТОР
description In the Kharkov Institute of Physics and Technology 225 MeV electron storage ring NESTOR is under development. The paper describes the design and parameters of a 700 MHz cavity that has been fabricated at BINP for the NESTOR RF-system. Now the low-power and vacuum tests of the cavity are under way at BINP. We present here the results of 3D simulations of the cavity with ANSYS code. The problem of multibunch instabilities in NESTOR is also discussed. В ННЦ ХФТІ споруджується електронне накопичувальне кільце НЕСТОР на енергію 225 МеВ. У роботі описується конструкція та приводяться параметри резонатора на 700 МГц, виготовленого в ІЯФ СВ РАН ім. Будкера для ВЧ-системи накопичувача. У дійсний час резонатор проходить вакуумні випробування та радіотехнічні вимірювання в ІЯФ. У роботі також приводяться результати 3D моделювання резонатору за допомогою програми ANSYS. Обговорюється також проблема багатозгусткових нестійкостей у накопичувачі НЕСТОР. В ННЦ ХФТИ сооружается электронное накопительное кольцо НЕСТОР на энергию 225 МэВ. В работе описывается конструкция и приводятся параметры резонатора на 700 МГц, изготовленного в ИЯФ СО РАН им. Будкера для ВЧ-системы накопителя. В настоящее время резонатор проходит вакуумные испытания и радиотехнические измерения в ИЯФ. В работе также приводятся результаты 3D моделирования резонатора с помошью программы ANSYS. Обсуждается также проблема много- сгустковых неустойчивостей в накопителе НЕСТОР.
issn 1562-6016
url https://nasplib.isofts.kiev.ua/handle/123456789/110565
citation_txt RF-cavity for the X-ray generator NESTOR / V.P. Androsov, K.N. Chernov, A.M. Gvozd, I.M. Karnaukhov, G.N. Ostreyko, I.K. Sedlyarov, Y.N. Telegin // Вопросы атомной науки и техники. — 2007. — № 5. — С. 151-155. — Бібліогр.: 9 назв. — англ.
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fulltext RF-CAVITY FOR THE X-RAY GENERATOR NESTOR V.P. Androsov1, K.N. Chernov2, A.M. Gvozd1, I.M. Karnaukhov1, G.N. Ostreyko2, I.K. Sedlyarov2, Yu.N. Telegin1∗ 1National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine 2Budker Institute of Nuclear Physics (BINP), Novosibirsk, Russia (Received March 13, 2007) In the Kharkov Institute of Physics and Technology 225 MeV electron storage ring NESTOR is under development. The paper describes the design and parameters of a 700 MHz cavity that has been fabricated at BINP for the NESTOR RF-system. Now the low-power and vacuum tests of the cavity are under way at BINP. We present here the results of 3D simulations of the cavity with ANSYS code. The problem of multibunch instabilities in NESTOR is also discussed. PACS: 29.20.Dh, 29.27.Bd 1. INTRODUCTION Beam dynamics simulations in NESTOR, Comp- ton scattering considered [1], have shown that for col- lision angle α=1700 and Nd laser (λlaser=1.06µm) beam parameters available in the nearest future (Elaser= 20µJ/pulse, frep=350 MHz) an impact of Compton scattering on the electron beam is negli- gible and the electron beam parameters are domi- nated by intrabeam scattering and turbulent bunch lengthening. To overcome these effects and to obtain a bunch length which would match a pulse width of the commercially available Nd mode-locked laser (∼7ps) one has to apply the accelerating voltage of ∼300 kV. This voltage will be provided with a single cell 700 MHz cavity. In order to eliminate troubles concerned multi- bunch instabilities it would be reasonable to use a HOM-damped cavity like that designed for VEPP-5 damping ring project [2]. But from financial lim- itations we had to restrict ourselves to a common undamped cavity. The cavity shape and design are similar to that of the HOM-damped one. For the present time this cavity is under low-power and vac- uum tests at BINP. Fig.1. Cross sectional view of the cavity 2. CAVITY DESIGN AND PARAMETERS Cavity design is presented in Fig.1. It is a cylin- drical cavity with wide flat nosecones and short beam-pipes to meet stringent requirements to the cavity length (30 cm). It has three ports placed equidistantly around the outer wall. The piston tuner moved with a step-motor is attached to the upper port. The coaxial coupler (70x20 mm, 75 Ω) with in- ∗Corresponding author. E-mail address: telegin@kipt.kharkov.ua PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2007, N5. Series: Nuclear Physics Investigations (48), p.151-155. 151 ductive loop is connected to the cavity through one of the lower ports. The third port houses a field probe and a sleeve for connecting a fore-pumping unit. On the cavity bottom the fourth port without body-size hole but with pumping slots for ion pump is located. Cavity beam-pipes have an elliptical cross section, 80mm x 29mm, that matches that of the vacuum chamber, and they end with membranes, 180 mm di- ameter and 1mm thick, for welding. Each sidewall is cooled through four concentric channels with rectangular cross section, 10x5 mm2, machined into the wall and covered with a lid by brazing. The outer wall is cooled via two exter- nal circumferential channels which present the flat pipes brazed to the wall. Each port and the recipro- cal flange are also provided with an external round channel. Additional cooling is provided for the tuner and coaxial coupler. Fig.2. View of the cavity The view of the cavity (with a mounted tuner) at fabrication stage before brazing the second side wall is given in Fig.2. The main cavity parameters are presented in Ta- ble 1. Table 1. RF-cavity parameters Parameter Value Frequency, frf , MHz 699.3 Frequency range, ∆f , MHz ± 0.8 Q-factor, Q ∼ 20000 Shunt impedance, Rsh, MΩ ∼ 4.5 Transit time factor, T 0.72 RF–voltage, V0, kV 250 Dissipated power, Pc, kW 15 Coupling factor, β 1.05−1.08 3. CAVITY SIMULATIONS The preliminary simulations with SUPERFISH [3] of the axially-symmetric cavity with a cell shape similar to that of the real one have revealed 8 monopole modes below 2.8 GHz (the cut-off fre- quency of the 80 mm circular beam-pipe), which were easily identified as TM010 (fundamental mode), TM011, TM012, TM020, TM021, TM013, TM022 and TM030 modes. Changing of the beam-pipe radius from 40 to 15 mm (the major and minor semiaxes of the beam-pipe cross section) led to the shift of fun- damental mode frequency of about 10 MHz and to shifts of HOM frequencies in the range of 0 – 30 MHz. It should be noted that, at the same time, shunt impedance of the fundamental mode was increased by 20 percents; HOM impedances did not changed essentially except that of TM021 mode. Longitudi- nal impedance of this mode was increased tree times and reached 1.86 MΩ (1/4 of the fundamental mode shunt impedance). The 3D simulations were performed with AN- SYS code [4] by using the cavity model presented in Fig.3. Considering cavity symmetry relative to the median plane, only half-cell was modelled. The model includes a tuner port with a piston in neutral position, a coupler port and a probe/forepumping port. The last two ports have different lengths in the model according to the design of corre- sponding joints. The pumping slots at the bot- tom of the cavity were not taken into account. Fig.3. The NESTOR cavity model (half-cell) for 3D simulations with applied mesh The ANSYS postprocessor outputs the following cavity parameters: mode frequency -f , Q-factor -Q and surface power losses -Pc. By using ’path oper- ation’ option one can calculate the following quanti- ties: 152 – voltage drop along the beam axis: V0 = ∣∣∣ ∫ l/2 −l/2 Exdx ∣∣∣ , (1) – transit time factor: T = 1 V0 ∣∣∣ ∫ l/2 −l/2 Ex exp jkxdx ∣∣∣ , (2) – longitudinal (shunt) impedance: R‖ = ZT 2 = V 2 0 Pc T 2 . (3) Transverse impedances - R⊥ were calculated by us- ing the following equation that is usually applied for derivation of R⊥ from experimental data in cold mea- surements [5]: R⊥= QZ0  j ∫ V E⊥exp(jkx)dx− ∫ V H⊥exp(jkx)dx   2 , (4) where k = 2πf and Z0 = (µ0/ε0)1/2 is characteris- tic vacuum impedance. Sixty three resonances were found in the frequency range below 2.5 GHz. Pa- rameters of the modes that can be of interest are presented in Table 2. The cavity model was built on basis of design drawings which take into account fabrication process with in-between frequency mea- surements and dimension corrections, so the funda- mental frequency was found to be lower than the design value. Boundary conditions, presented in the second column, correspond to electric (E) or mag- netic (M) wall on symmetry plane and beam-pipe flank. Table 2. Cavity modes f , BC Q R‖, R⊥, Mode MHz ·104 MΩ MΩ/m origin 695.0 EE 2.96 7.31 TM010 1008.3 ME 3.07 0.05 0.1 TE (v) 111 1022.1 ME 3.16 1.2 TE (h) 111 1017.9 ME 2.51 0.94 TM011 1183.7 EE 3.95 2.7(v) TM (1) 110 5.5(h) 1185.6 EE 4.16 0.7(v) TM (2) 110 20.4(h) 1234.8 ME 3.55 TE (1) 211 1257.5 ME 3.68 TE (2) 211 1458.7 ME 3.04 43.3 TM (v) 111 1491.0 ME 3.54 20.3 TM (h) 111 1572.6 ME 3.40 TE311 1606.7 EE 4.26 TM (1) 210 1627.8 EE 4.65 TM (2) 210 1668.3 EE 3.42 TM012 1700.5 EE 3.41 0.02 5.5 TE (h) 112 1717.2 EE 3.63 0.11 12.9 TE (v) 112 1760.0 EE 4.60 0.24 TM020 2009.5 ME 3.28 1.68 TM021 The general notes are the following: – each dipole mode splits into two modes - hori- zontal and vertical, as a rule; – quadrupole modes split too, giving pairs with a similar field pattern but turned around the X-axis by 450; – the pairs of modes with 3 azimuth variations and some other exotic modes appear; – the longitudinal HOM-impedances well agree with SUPERFISH results, both reveal TM021 mode with R‖=1.7 MΩ will be potentially dangerous. The examples of calculated field patterns are given in Fig. 4 which illustrates dipole mode split- ting when an azimuthal field pattern is influenced by the cavity ports (modes can not be defined as vertical and horizontal). For these modes two components of R⊥, horizontal (h) and vertical (v), are presented in the tables. In the Table 3 the obtained values R‖/Q and R⊥/Q for the most dangerous monopole and dipole modes are compared with those for the room- temperature cavities exploited in the course of many years in well-known electron storage rings. The table shows that NESTOR cavity has the highest R‖/Q value of the fundamental mode (due to low cross sec- tion of beam-pipes). It has also the lowest R‖/Q value of TM011 mode while the highest R‖/Q value of TM021. Fig.4. Azimuthal distribution of the electric field for dipole modes 1183.7 MHz and 1185.6 MHz 153 Table 3. A comparison of the calculated factors R‖/Q (R⊥/Q) for the most prominent monopole (dipole) modes in different cavities SRS [6] KEK-PF [7] ATF DR [8] a NESTOR (MAFIA 3D) (URMEL 2D) (MAFIA 3D) (ANSYS 3D) f, R‖/Q(R⊥/Q), f, b R‖/Q(R⊥/Q), f, R‖/Q(R⊥/Q), f, R‖/Q(R⊥/Q), MHz Ω (Ω/m) MHz Ω (Ω/m) MHz Ω (Ω/m) MHz Ω (Ω/m) Monopole modes TM010 498.8 195 500.1 175 724.7 169 695.0 247 TM011 809.5 68 793.0 52 1044 62 1017.9 37 TM021 1333.0 11 1371.0 9 1959 7 2009.5 51 Dipole modes TM (1) 110 791.5 220 789.7 248 1152 263 1183.7 68(v) 139(h) TM (2) 110 797.1 255 792.6 1185.6 17(v) 490(h) TM (v) 111 1059.2 566 988.8 449 1349 726 1458.7 1424 TM (h) 111 1059.3 568 989.8 1491.0 573 aHOM-damped cavity, HOM-waveguides shorted. bExperimental values. It should be noted that though the calculations for the ATF DR HOM-damped cavity were performed with 3D code MAFIA, the axially symmetric cav- ity was considered (if not taking into account HOM waveguides), so dipole mode splitting is not present in the table, like in the case of KEK PF cavity, sim- ulated with 2D code URMEL. The comparison of R⊥/Q for the dipole modes show that results for NESTOR cavity averaged over a number of split modes are within the range of R⊥/Q values given for other cavities except that for TM (h) 111 mode. The analysis of the axial field distribution shows that the large value of R⊥/Q for this mode is accounted for by penetration of the field into a beam-pipe (verti- cal component of the electric field is high along the beam-pipe axis). In the view of multibunch instabilities only modes trapped in the cavity are dangerous. Because the cavity shape is close to a pill-box and the beam- pipe cross section is elliptical, it isn’t easy to calcu- late a cut-off frequency for beam-pipes. Simulations show that a number of trapped modes is large, and the problem of multibunch instabilities is vital for NESTOR ring. The conservative estimates for coupled-bunch in- stabilities in NESTOR, obtained with traditional rigid-bunch approximation formulas [5], give the threshold bunch currents in the microampere range. These values are much lower than the designed value of 10 mA/bunch. We suppose to use the HOM tuning technique based on variation of cavity temperature [9] to cure these instabilities. 4. CONCLUSION The 700 MHz accelerating cavity for the RF- system of electron storage ring NESTOR has been fabricated in BINP. Cavity simulations show that a large number of trapped modes with perceptible coupling impedances can essentially complicate beam storing in NESTOR. The most dangerous are dipole modes (TM110-like and TM111-like). REFERENCES 1. P. Gladkikh, I. Karnaukhov, A. Mytsykov et al. The Operation Modes of Kharkov X-ray Gen- erator based on Compton Scattering NESTOR // European Particle Accelerator Conf. Luzern, Switzerland, 2004, p. 1428 – 1430. 2. N. Alinovsky, D. Bolkhovityanov, V. Dolgashev et al. RF system for VEPP-5 damping ring // European Particle Accelerator Conf. Stockholm, Sweden, 1998, p. 1799 – 1801. 3. J.H. Billen and L.M. Young. POISSON/ SUPER- FISH on PC Compatibles // Particle Accelerator Conf. Washington, USA, 1993, p. 790 – 792. 4. http://www.ansys.com 5. Y. Yamazaki, K. Takata, S. Tokumoto. Damping test of the higher-order modes of the re-entrant accelerating cavity // IEEE Trans., 1981, NS28, p.2915–2917. 6. J.N. Corlett. Higher order modes in the SRS 500 MHz accelerating cavities: Preprint. Daresbury Laboratory, DL/SCI/P627A, 1989, 3 p. 7. N. Koseki, M. Izawa and Y. Kamiya. Develop- ment of a damped cavity with SiC beam duct // Particle Accelerator Conf. Dallas, USA, 1995, p.1791 - 1793. 8. S. Sakanaka, K. Kubo and T. Higo. Design of HOM damped cavity for the ATF damping ring // Particle Accelerator Conf. Dallas, USA, 1995, p.1027 - 1729. 154 9. H. Kobayakawa, M. Izagawa, S. Sakanaka and S.Tokumoto. Suppression of beam insta- bilities induced by accelerating cavities // Rev.Sci.Instrum., 1989, v.60, p.1732–1735. ВЧ-РЕЗОНАТОР ДЛЯ ГЕНЕРАТОРА РЕНТГЕНОВСКОГО ИЗЛУЧЕНИЯ НЕСТОР В.П. Андросов, К.Н. Чернов, А.М. Гвоздь, И.М. Карнаухов, Г.Н. Острейко, И.К. Седляров, Ю.Н. Телегин В ННЦ ХФТИ сооружается электронное накопительное кольцо НЕСТОР на энергию 225 МэВ. В работе описывается конструкция и приводятся параметры резонатора на 700 МГц, изготовленного в ИЯФ СО РАН им. Будкера для ВЧ-системы накопителя. В настоящее время резонатор проходит вакуумные испытания и радиотехнические измерения в ИЯФ. В работе также приводятся результаты 3D моделирования резонатора с помошью программы ANSYS. Обсуждается также проблема много- сгустковых неустойчивостей в накопителе НЕСТОР. ВЧ-РЕЗОНАТОР ДЛЯ ГЕНЕРАТОРА РЕНТГЕНIВСЬКОГО ВИПРОМIНЮВАННЯ НЕСТОР В.П. Андросов, К.М. Чернов, А.М. Гвоздь, I.М. Карнаухов, Г.М. Острейко, I.К. Седляров, Ю.М. Телегiн В ННЦ ХФТI споруджується електронне накопичувальне кiльце НЕСТОР на енергiю 225 МеВ. У роботi описується конструкцiя та приводяться параметри резонатора на 700 МГц, виготовленого в IЯФ СВ РАН iм. Будкера для ВЧ-системи накопичувача. У дiйсний час резонатор проходить ваку- умнi випробування та радiотехнiчнi вимiрювання в IЯФ. У роботi також приводяться результати 3D моделювання резонатору за допомогою програми ANSYS. Обговорюється також проблема багатозгуст- кових нестiйкостей у накопичувачi НЕСТОР. 155