- Email: [email protected]
Realized parameters of KSRS storage rings
Nima 20607
Bala
Vijaya
Mini
Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
Realized parameters of KSRS storage rings A.V. Filipchenko , V.N. Korchuganov *, V.A. Ushakov , Yu.V. Krylov, V.L. Ushkov, A. Valentinov, Yu.L. Yupinov Budker Institute of Nuclear Physics, Lavrentyev. ave.11, 630090 Novosibirsk, Russia Russian Research Center **Kurchatov Institute++, Moscow, Russia
Abstract Kurchatov Synchrotron Radiation Source (KSRS), the "rst dedicated SR facility in Russia, is preparing to start regular experiments with hard X-rays. The facility, designed and manufactured in collaboration with Budker INP, includes 450 MeV booster storage ring SIBERIA-1 and 2.5 GeV storage ring SIBERIA-2. Booster storage ring SIBERIA-1 is also used as an independent light source with three beamlines. The paper describes the realized electron beam parameters of SIBERIA-1 and SIBERIA-2 in di!erent modes and operational characteristics of these storage rings. 2000 Published by Elsevier Science B.V. All rights reserved. PACS: 29.20.Dh; 29.20.-c; 29.27.Bd; 29.90.#r Keywords: Storage ring; Emittance; Synchrotron radiation; Brightness
1. Introduction Kurchatov Synchrotron Radiation Source (KSRS) is the "rst dedicated synchrotron radiation facility in Russia. It was designed in the Budker Institute of Nuclear Physics [1]. The facility includes two storage rings } 450 MeV SIBERIA-1 and 2.5 GeV SIBERIA-2. They are intended for experiments in the 0.1}2000 As range of SR wavelengths. SIBERIA-1 is in operation since 1992 in a new building. First electron beam in SIBERIA-2 at
* Corresponding author. Tel.: #7-3832-394238; fax: 7-3832342163. E-mail address: [email protected] (V.N. Korchuganov).
450 MeV was observed in 1995. In 1996 SIBERIA2 reached 2.5 GeV with 10 mA current [2]. A great progress was achieved in increasing SIBERIA-2 stored current during last year. Now maximum current at injection energy is 142 mA in multibunch mode and 59 mA in single-bunch mode. Maximum current obtained at 2.5 GeV is 72 mA. Outgassing of vacuum chamber by SR is in progress in order to increase beam lifetime. Machine characteristics and beam parameters of both storage rings are described below. First part of SR beamline from bending magnet was installed outside biological shielding in an experimental hall of SIBERIA-2. We plan to install four beamlines and start regular experiments with hard X-rays at the beginning of 1999. SIBERIA-1 experimental hall with three beamlines and three experimental stations is also ready for experiments.
0168-9002/00/$ - see front matter 2000 Published by Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 9 ) 0 0 7 4 0 - 8
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
9
Table 1 General parameters of SIBERIA-1 Energy Field in bending magnets Circumference Betatron tunes Q , Q V X Relative energy spread, rms Horizontal emittance Vertical emittance Natural chromaticity m , m V X Momentum compaction factor Damping times q , q , q V X Q RF harmonic number RF frequency Maximum current Beam dimensions in SIBERIA-1 radiation point
0.45 GeV 1.5 T 8.68 m 0.82, 0.85 3.8;10\ 7.9;10\ m rad 7.9;10\ m rad !1.9, 0.9 1.506 7.5, 7.2, 3.4 ms 1 34.52 MHz 210 mA p "0.142 mm, p "0.67 mrad; V VY p "0.012 mm, p "0.068 mrad X XY
2. SIBERIA-1 Linear accelerator with an energy of 75}80 MeV provides injection to SIBERIA-1 one time per second. The SIBERIA-1 storage ring is capable of providing 30 s cycle of injection to SIBERIA-2 with 120}140 mA current. Both beam injection and beam extraction are done in vertical plane. During last year we reduced ramping time in SIBERIA-1 from 20 s down to 7 s. This fact provided a possibility of making injection process more fast and stable. Ramping time is limited by the maximum tuning speed of RF cavity. Main parameters of SIBERIA-1 are given in Table 1. Table 1 also contains electron beam dimensions for radiation point in the center of the bending magnet.
Fig. 1. SIBERIA-2 half-cell optical functions.
Table 2 General parameters of SIBERIA-2 Energy Field in bending magnets Circumference Number of cells Betatron tunes Q , Q V X Relative energy spread, rms Horizontal emittance Natural chromaticity m , m V X Momentum compaction factor Damping times q , q , q V X Q RF harmonic number RF frequency Maximum design current, multi-bunch mode
2.5 GeV 1.7 T 124.13m 6 7.775, 6.695 9.53;10\ 98 nm.rad !16.7, !12.9 0.0104 2.92, 3.04, 1.55 ms 75 181.14 MHz 300 mA
parameters are shown "nd in Table 2. These parameters were calculated using real currents of magnet power supplies and results of magnetic measurements.
3. SIBERIA-2
3.2. Injection
3.1. Magnetic structure
The electrons are injected into SIBERIA-2 in horizontal plane during one turn. Before injection the orbit of a stored beam is disturbed and moved to a septum magnet by means of the fast horizontal kickers. Only one of 75 buckets can be "lled during one injection cycle. Typically 5}6 mA is added to SIBERIA-2 current after each cycle of injection. Injection e$ciency depends on RF voltage. It
SIBERIA-2 has magnetic structure of modi"ed DBA type. It is optimized to obtain intensive spectral #ux and to reach high spectral brightness of SR from radiation points situated both in bending magnets and in insertion devices. Optical functions of SIBERIA-2 lattice are shown in Fig. 1. Basic
SECTION I.
10
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
equals 90%}94% when ; is below 70 kV and slowly decreases with growing ; . Such a behavior corresponds to energy aperture of approximately 1%. We note that a kicker pulse duration is no less than 15 ns at half-level and is larger than 5.5 ns time interval between bunches. In spite of this fact injection to neighbouring backets with high e$ciency is possible because of high time stability of kicker pulses (rms jitter are near to 1 ns). It was found that maximum stored current in multi-bunch and single-bunch modes is not restricted by injection system operation. 3.3. Single-bunch mode We achieved 59 mA in single-bunch mode at injection energy. Above 40 mA longitudinal instability was observed by phase dissector. This instability leads to lifetime shortening and saturation of stored current. Maximum current value depends on RF generator tuning. We also observed strong lengthening of bunch with current (Fig. 2). The behavior of bunch length corresponds to longitudinal coupling impedance of vacuum chamber walls equal to approximately 8.6 ). It may be caused by imperfections of vacuum chamber and HOM of RF cavities. 3.4. Multi-bunch mode Maximum current stored in multi-bunch mode now equals 142 mA. At the end of injection process
Fig. 2. Dependence of longitudinal RMS beam size on electron current in single-bunch mode.
every bunch contains 3}4 mA; a number of the bunches can reach 30}35. At present it takes nearly 20 mins to store 130 mA; so "rst bunches have su$cient time to lose 40%}50% of electrons. Maximum current is limited by multibunch coherent longitudinal instabilities observed by dissector. A threshold of instability appearing depends on RF voltage. For example, we can store 60}70 mA with ; "100 kV, but 130 mA need 200}210 kV. Unfortunately it leads to decreasing of injection e$ciency, as mentioned above. Below 100 mA appeared instability can be damped by raising ; . Above 100 mA the instability can lead to increasing of transverse beam size and "nally to sharp beam losses. 3.5. Energy ramping An energy ramping time was reduced from 6 mins down to 2 min 40 s during 1997. Now maximum ramping speed is 22 MeV/s. Ramping procedure is rather complicated and includes 9 intermediate levels of energy that can be tuned separately [3]. The main problem is to keep betatron tune shifts under acceptable tolerances during ramping. Normally SIBERIA-2 operates with betatron tunes Q "7.775 and Q "6.695. Nearest V X dangerous resonances in this case are sum resonances of fourth order: 2Q #2Q "29 and V X 3Q #Q "30. These resonances are dangerous V X below 0.9 GeV and can cause beam losses. There is no loss above 1 GeV. Betatron tunes are measured by resonance excitation of beam by special coil. To keep the initial values of betatron tunes after a long stop or after high energy run we use special magnetization loop of main magnetic elements [3]. Ramping e$ciency is usually equal to 85%}90%. Most part of losses is caused by short beam lifetime at the energies below 1 GeV. Maximum current registered at 2.5 GeV was 72 mA in multi-bunch mode starting from 83 mA at injection energy. E$ciency of ramping depends on bunch behavior. If longitudinal instability (see above) takes place the e$ciency is decreased rapidly. For example, we could not accelerate more than 20 mA in single-bunch mode due to this fact. Maximum value of accelerated current is restricted by RF power available now. The RF
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
11
Table 3 Electron beam dimensions in SIBERIA-2 radiation points (rms) Radiation points
Horizontal size (mm)
Horizontal divergence (mrad)
Vertical size (mm)
Vertical divergence (mrad)
Bending magnet M1 Bending magnet M2 Bending magnet M3 Bending magnet M4 Wiggler straight section Undulator straight section
0.55 0.31 0.33 0.48 0.63 1.53
0.30 0.42 0.38 0.26 0.16 0.09
0.109 0.062 0.083 0.077 0.034 0.110
0.054 0.043 0.043 0.054 0.058 0.018
system of SIBERIA-2 includes two accelerating cavities, two waveguides and two RF generators operating at 181.14 MHz. At present one RF generator and one RF cavity are in operation. Routine work is done with 1.2 MV at 2.5 GeV. The second RF cavity is also tested and installed on the ring. Commissioning of second RF generator is planned during autumn 1998. We hope to achieve 100 mA at 2.5 GeV by the end of 1998 and then design value of 300 mA after the tuning of RF system. 3.6. Lifetime
magnets (8 - horizontal and 5- vertical) used for COD correction. Maximum CODs are equal to 2 mm in horizontal direction and 1 mm in vertical direction at injection energy. These "gures are slightly more at 2.5 GeV. Coupling factor (that is vertical to horizontal emittance ratio) measurement gave K"0.02. For natural chromaticity compensation we used two families of sextupole lenses located inside achromatic bend. Harmonic sextupoles were not switched on. At present we work at m "m "#0.7. V W 3.8. Beam dimensions
Electron beam lifetime depends mainly on vacuum conditions. Vacuum pressure is equal to 10\ Torr without beam and lifetime is equal to 2.5 h with 10 mA beam. The pressure increases by almost two orders of magnitude with 50}60 mA beam. We need to continue outgassing of vacuum chamber by SR beam in order to improve vacuum conditions and lifetime. Now, we have achieved 3.7 A h of current integral at 2.5 GeV. At injection energy the life time is much less. For example, single 5 mA bunch has a lifetime of 35 min, but lifetime is almost independent of current and equals to 22}25 mins for more than 5 bunches. 3.7. Closed orbit destortion (COD) and chromaticity Operation at designed revolution frequency f "2.41519 MHz provides maximum injection e$ciency and decreases a number of correction
It is planned to use a synchrotron radiation both from bending magnets and from insertion devices at SIBERIA-2. Magnet lattice contains 9 straight sections for wigglers (low b-functions, small beam size) and undulators (high b-functions, small angle divergence). Table 3 shows beam dimensions for all types of radiation points. Measured coupling coef"cient K"0.02 was used to calculate vertical beam dimensions.
References [1] V.V. Anashin et al., Nucl. Instr. and Meth. A 282 (1989) 369. [2] V.N. Korchuganov et al., The EPAC'96 Proceedings, Vol. 1, Sitges, Spain, 1996, p. 608. [3] V.N. Korhuganov et al., The EPAC'96 Proceedings, Vol. 2, Sitges, Spain, 1996, p. 1426.
SECTION I.
Bala
Vijaya
Mini
Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
Realized parameters of KSRS storage rings A.V. Filipchenko , V.N. Korchuganov *, V.A. Ushakov , Yu.V. Krylov, V.L. Ushkov, A. Valentinov, Yu.L. Yupinov Budker Institute of Nuclear Physics, Lavrentyev. ave.11, 630090 Novosibirsk, Russia Russian Research Center **Kurchatov Institute++, Moscow, Russia
Abstract Kurchatov Synchrotron Radiation Source (KSRS), the "rst dedicated SR facility in Russia, is preparing to start regular experiments with hard X-rays. The facility, designed and manufactured in collaboration with Budker INP, includes 450 MeV booster storage ring SIBERIA-1 and 2.5 GeV storage ring SIBERIA-2. Booster storage ring SIBERIA-1 is also used as an independent light source with three beamlines. The paper describes the realized electron beam parameters of SIBERIA-1 and SIBERIA-2 in di!erent modes and operational characteristics of these storage rings. 2000 Published by Elsevier Science B.V. All rights reserved. PACS: 29.20.Dh; 29.20.-c; 29.27.Bd; 29.90.#r Keywords: Storage ring; Emittance; Synchrotron radiation; Brightness
1. Introduction Kurchatov Synchrotron Radiation Source (KSRS) is the "rst dedicated synchrotron radiation facility in Russia. It was designed in the Budker Institute of Nuclear Physics [1]. The facility includes two storage rings } 450 MeV SIBERIA-1 and 2.5 GeV SIBERIA-2. They are intended for experiments in the 0.1}2000 As range of SR wavelengths. SIBERIA-1 is in operation since 1992 in a new building. First electron beam in SIBERIA-2 at
* Corresponding author. Tel.: #7-3832-394238; fax: 7-3832342163. E-mail address: [email protected] (V.N. Korchuganov).
450 MeV was observed in 1995. In 1996 SIBERIA2 reached 2.5 GeV with 10 mA current [2]. A great progress was achieved in increasing SIBERIA-2 stored current during last year. Now maximum current at injection energy is 142 mA in multibunch mode and 59 mA in single-bunch mode. Maximum current obtained at 2.5 GeV is 72 mA. Outgassing of vacuum chamber by SR is in progress in order to increase beam lifetime. Machine characteristics and beam parameters of both storage rings are described below. First part of SR beamline from bending magnet was installed outside biological shielding in an experimental hall of SIBERIA-2. We plan to install four beamlines and start regular experiments with hard X-rays at the beginning of 1999. SIBERIA-1 experimental hall with three beamlines and three experimental stations is also ready for experiments.
0168-9002/00/$ - see front matter 2000 Published by Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 9 ) 0 0 7 4 0 - 8
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
9
Table 1 General parameters of SIBERIA-1 Energy Field in bending magnets Circumference Betatron tunes Q , Q V X Relative energy spread, rms Horizontal emittance Vertical emittance Natural chromaticity m , m V X Momentum compaction factor Damping times q , q , q V X Q RF harmonic number RF frequency Maximum current Beam dimensions in SIBERIA-1 radiation point
0.45 GeV 1.5 T 8.68 m 0.82, 0.85 3.8;10\ 7.9;10\ m rad 7.9;10\ m rad !1.9, 0.9 1.506 7.5, 7.2, 3.4 ms 1 34.52 MHz 210 mA p "0.142 mm, p "0.67 mrad; V VY p "0.012 mm, p "0.068 mrad X XY
2. SIBERIA-1 Linear accelerator with an energy of 75}80 MeV provides injection to SIBERIA-1 one time per second. The SIBERIA-1 storage ring is capable of providing 30 s cycle of injection to SIBERIA-2 with 120}140 mA current. Both beam injection and beam extraction are done in vertical plane. During last year we reduced ramping time in SIBERIA-1 from 20 s down to 7 s. This fact provided a possibility of making injection process more fast and stable. Ramping time is limited by the maximum tuning speed of RF cavity. Main parameters of SIBERIA-1 are given in Table 1. Table 1 also contains electron beam dimensions for radiation point in the center of the bending magnet.
Fig. 1. SIBERIA-2 half-cell optical functions.
Table 2 General parameters of SIBERIA-2 Energy Field in bending magnets Circumference Number of cells Betatron tunes Q , Q V X Relative energy spread, rms Horizontal emittance Natural chromaticity m , m V X Momentum compaction factor Damping times q , q , q V X Q RF harmonic number RF frequency Maximum design current, multi-bunch mode
2.5 GeV 1.7 T 124.13m 6 7.775, 6.695 9.53;10\ 98 nm.rad !16.7, !12.9 0.0104 2.92, 3.04, 1.55 ms 75 181.14 MHz 300 mA
parameters are shown "nd in Table 2. These parameters were calculated using real currents of magnet power supplies and results of magnetic measurements.
3. SIBERIA-2
3.2. Injection
3.1. Magnetic structure
The electrons are injected into SIBERIA-2 in horizontal plane during one turn. Before injection the orbit of a stored beam is disturbed and moved to a septum magnet by means of the fast horizontal kickers. Only one of 75 buckets can be "lled during one injection cycle. Typically 5}6 mA is added to SIBERIA-2 current after each cycle of injection. Injection e$ciency depends on RF voltage. It
SIBERIA-2 has magnetic structure of modi"ed DBA type. It is optimized to obtain intensive spectral #ux and to reach high spectral brightness of SR from radiation points situated both in bending magnets and in insertion devices. Optical functions of SIBERIA-2 lattice are shown in Fig. 1. Basic
SECTION I.
10
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
equals 90%}94% when ; is below 70 kV and slowly decreases with growing ; . Such a behavior corresponds to energy aperture of approximately 1%. We note that a kicker pulse duration is no less than 15 ns at half-level and is larger than 5.5 ns time interval between bunches. In spite of this fact injection to neighbouring backets with high e$ciency is possible because of high time stability of kicker pulses (rms jitter are near to 1 ns). It was found that maximum stored current in multi-bunch and single-bunch modes is not restricted by injection system operation. 3.3. Single-bunch mode We achieved 59 mA in single-bunch mode at injection energy. Above 40 mA longitudinal instability was observed by phase dissector. This instability leads to lifetime shortening and saturation of stored current. Maximum current value depends on RF generator tuning. We also observed strong lengthening of bunch with current (Fig. 2). The behavior of bunch length corresponds to longitudinal coupling impedance of vacuum chamber walls equal to approximately 8.6 ). It may be caused by imperfections of vacuum chamber and HOM of RF cavities. 3.4. Multi-bunch mode Maximum current stored in multi-bunch mode now equals 142 mA. At the end of injection process
Fig. 2. Dependence of longitudinal RMS beam size on electron current in single-bunch mode.
every bunch contains 3}4 mA; a number of the bunches can reach 30}35. At present it takes nearly 20 mins to store 130 mA; so "rst bunches have su$cient time to lose 40%}50% of electrons. Maximum current is limited by multibunch coherent longitudinal instabilities observed by dissector. A threshold of instability appearing depends on RF voltage. For example, we can store 60}70 mA with ; "100 kV, but 130 mA need 200}210 kV. Unfortunately it leads to decreasing of injection e$ciency, as mentioned above. Below 100 mA appeared instability can be damped by raising ; . Above 100 mA the instability can lead to increasing of transverse beam size and "nally to sharp beam losses. 3.5. Energy ramping An energy ramping time was reduced from 6 mins down to 2 min 40 s during 1997. Now maximum ramping speed is 22 MeV/s. Ramping procedure is rather complicated and includes 9 intermediate levels of energy that can be tuned separately [3]. The main problem is to keep betatron tune shifts under acceptable tolerances during ramping. Normally SIBERIA-2 operates with betatron tunes Q "7.775 and Q "6.695. Nearest V X dangerous resonances in this case are sum resonances of fourth order: 2Q #2Q "29 and V X 3Q #Q "30. These resonances are dangerous V X below 0.9 GeV and can cause beam losses. There is no loss above 1 GeV. Betatron tunes are measured by resonance excitation of beam by special coil. To keep the initial values of betatron tunes after a long stop or after high energy run we use special magnetization loop of main magnetic elements [3]. Ramping e$ciency is usually equal to 85%}90%. Most part of losses is caused by short beam lifetime at the energies below 1 GeV. Maximum current registered at 2.5 GeV was 72 mA in multi-bunch mode starting from 83 mA at injection energy. E$ciency of ramping depends on bunch behavior. If longitudinal instability (see above) takes place the e$ciency is decreased rapidly. For example, we could not accelerate more than 20 mA in single-bunch mode due to this fact. Maximum value of accelerated current is restricted by RF power available now. The RF
A.V. Filipchenko et al. / Nuclear Instruments and Methods in Physics Research A 448 (2000) 8}11
11
Table 3 Electron beam dimensions in SIBERIA-2 radiation points (rms) Radiation points
Horizontal size (mm)
Horizontal divergence (mrad)
Vertical size (mm)
Vertical divergence (mrad)
Bending magnet M1 Bending magnet M2 Bending magnet M3 Bending magnet M4 Wiggler straight section Undulator straight section
0.55 0.31 0.33 0.48 0.63 1.53
0.30 0.42 0.38 0.26 0.16 0.09
0.109 0.062 0.083 0.077 0.034 0.110
0.054 0.043 0.043 0.054 0.058 0.018
system of SIBERIA-2 includes two accelerating cavities, two waveguides and two RF generators operating at 181.14 MHz. At present one RF generator and one RF cavity are in operation. Routine work is done with 1.2 MV at 2.5 GeV. The second RF cavity is also tested and installed on the ring. Commissioning of second RF generator is planned during autumn 1998. We hope to achieve 100 mA at 2.5 GeV by the end of 1998 and then design value of 300 mA after the tuning of RF system. 3.6. Lifetime
magnets (8 - horizontal and 5- vertical) used for COD correction. Maximum CODs are equal to 2 mm in horizontal direction and 1 mm in vertical direction at injection energy. These "gures are slightly more at 2.5 GeV. Coupling factor (that is vertical to horizontal emittance ratio) measurement gave K"0.02. For natural chromaticity compensation we used two families of sextupole lenses located inside achromatic bend. Harmonic sextupoles were not switched on. At present we work at m "m "#0.7. V W 3.8. Beam dimensions
Electron beam lifetime depends mainly on vacuum conditions. Vacuum pressure is equal to 10\ Torr without beam and lifetime is equal to 2.5 h with 10 mA beam. The pressure increases by almost two orders of magnitude with 50}60 mA beam. We need to continue outgassing of vacuum chamber by SR beam in order to improve vacuum conditions and lifetime. Now, we have achieved 3.7 A h of current integral at 2.5 GeV. At injection energy the life time is much less. For example, single 5 mA bunch has a lifetime of 35 min, but lifetime is almost independent of current and equals to 22}25 mins for more than 5 bunches. 3.7. Closed orbit destortion (COD) and chromaticity Operation at designed revolution frequency f "2.41519 MHz provides maximum injection e$ciency and decreases a number of correction
It is planned to use a synchrotron radiation both from bending magnets and from insertion devices at SIBERIA-2. Magnet lattice contains 9 straight sections for wigglers (low b-functions, small beam size) and undulators (high b-functions, small angle divergence). Table 3 shows beam dimensions for all types of radiation points. Measured coupling coef"cient K"0.02 was used to calculate vertical beam dimensions.
References [1] V.V. Anashin et al., Nucl. Instr. and Meth. A 282 (1989) 369. [2] V.N. Korchuganov et al., The EPAC'96 Proceedings, Vol. 1, Sitges, Spain, 1996, p. 608. [3] V.N. Korhuganov et al., The EPAC'96 Proceedings, Vol. 2, Sitges, Spain, 1996, p. 1426.
SECTION I.