ERL Prototype at BNL Ilan Ben-Zvi, for the Superconducting Accelerator and Electron Cooling group, Collider-Accelerator Department Brookhaven National Laboratory & Center for Accelerator Science and Education Stony Brook University 14 th International Conference on RF Superconductivity Berlin, September 20-25, 2009 Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Motivation: ERL based erhic erhic, High energy and luminosity -Polarized 20 GeV e - x 325 GeV p, -Linac e-current 500mA - Luminosity: ~ 10 33-10 34 cm -2 sec -1 MeRHIC: Medium Energy erhic -4GeV e - x 250 GeV p - Linac e-current 300mA - Luminosity ~10 32-10 33 cm -2 sec -1
SCA & EC Group activities Establishment of SRF infrastructure Polarized electron guns SRF polarized electron gun DC polarized electron gun erhic R&D SRF Electron guns (with photocathodes, laser) 1.3 GHz, 704 MHz, 112 MHz ERL accelerating cavities at 704 MHz (erhic, SPL, ESS) The R&D ERL RHIC SRF cavities 56 MHz store cavity 28 MHz accelerating cavity Electron cooling Low Energy RHIC electron cooling Coherent electron cooling for RHIC and erhic
Niobium chemistry Cutting edge technology, large cavity capability In collaboration and located at Advanced Energy Systems Inc.
Vertical Test Facility VTF complements chemistry facility Dewar 38 diameter 96 working depth RF systems from 56 1300 MHz LHe refrigerator with 360 W capacity, 1000 gallon storage Dewar Liquid ring pump for operation to 1.8K
The BNL High-Current R&D ERL Aimed at pushing the limits for beam current: 0.5 amperes Testing of novel components and techniques: Superconducting electron gun Diamond amplified photocathode Z-bend ERL beam merging High-current SRF cavity at 703.75 MHz Diagnostics and more. Working with industry (AES) on many aspects
ERL layout
ERL Beam Design Parameters R&D ERL design BNL ERL projects requirements High Current High charge PoP CeC Test *) Pre-cooling @ 40GeV MEeRHIC erhic 10/20 Charge per bunch, nc 0.7 5 5 5 14 (9x1.56) 5 18/3.5 Energy maximum/injection, MeV 20/2.5 20/3.0 21/3 21/3 21/3 4000/5 10000/5 20000/5 R.m.s. Normalized emittances ex/ey, mm*mrad 1.4/1.4 4.8/5.3 5 5 3 7-73 77 R.m.s. Energy spread, de/e 3.5x10-3 1x10-2 1.5x 10-3 1.5x 10-3 8 10-4 2x10-3 1x10-3 R.m.s. Bunch length, ps 18 31 30 30 30 6.7 30 Bunch rep-rate, MHz 700 9.383 0.078 9.383 9.383 9.383 14.1 Gun/dumped ave. current, ma 500 50 0.4 50 130 50 260/50 Linac average current, ma 500 50 0.4 0.4/50 130 300 2600/500 Injected/ejected beam power, MW 1.0 0.150 0.0012 0.15 0.390 0.250 1.3/0.250 Numbers of passes 1 1 1 1 1 3 5
High-current SRF electron-gun ½ Cell SRF injector Demountable cathode stalk HTS Solenoid UHV load-lock cathode MW twin couplers
Internal Helium dewar Cryomodule Configuration Top cover with facilities feedthru Cathode isolation Valve Cavity assembly Cathode installation assembly Magnetic and thermal shielding Adjustable supports Beam line isolation valve HOM Load Power coupler
Tuner and cathode clamp
High Temperature Superconducting Solenoid for focusing
Laser System Lumera built a 5 W, 355 nm, 10 ps, 9.38 MHz laser system Designed for BNL needs for generation of 50 ma current We had discussions with vendor about upgrading to system for 500 ma if funding is available Will be operated at 532nm, 355nm, and 266nm Active program for generation of spatial and temporal flat top beams underway with good progress System in place.
Photocathode laser constructed LUMERA LASER GmbH, Germany RPMC Laser Inc, USA. 9.4 MHz rep rate Nd:YVO 4 ps MOPA with THG 355 nm End-pumped oscillator Fiber-coupled Very rigid with no tuning elements 800 µm pump diam. Ultra-stable amplifier
Photocathode R&D 5% in green, at high current density (doubled YAG) QE at 355 nm is 19%!
Multi-alkaline Photocathode Preparation and Load-Lock 3 rd Gen Deposition System 2 transporter carts delivered Base pressure 1x10-10 Torr System designed to eliminate cross contamination of sources Provides for quicker source exchange Transporter cart 2 UHV systems with LN 2 cooling capability Baking to improve vacuum
Diamond amplified photocathode
First observed beam from diamond amplified cathode 22mm Without focusing With focusing and reduced primary current Gain of 40 was measured in our current test conditions.
The High-current ERL Cavity BNL/AES All monopole and dipole HOMs propagate into the beam pipes, no trapped modes. Fundamental mode is evanescent in beam pipes. Large apertures, low frequency reduces HOM power and provides strong cell-to-cell coupling. Short cavity-to-cavity transitions can be made with a variety of HOM probes. The cavity is stiff (actually too stiff) and stable. Good performance measured in prototype.
The BNL-I 703.75 5-cell ERL Cavity H O M f e r r it e S p a c e f r a m e 4Ó R F s h ie ld e d T u n e r lo c a t 2io K n m a in lin e a s s e m b ly s u p p o r t s t r u c t u r e g a t e v a lv e C a v it y a s s e m b ly V a c u u m v e s s e l 2 K f il lin e O u t e r m a g n e t ic s h ie ld H e v e s s e l T h e r m a l s h ie ld I n n e r m a g n e t ic s h ie ld F u n d a m e n t a l P o w e r C o u p le r a s s e m b ly
Multipass transverse BBU 5 pass 10 GeV Beam Breakup as a function of the HOM frequency spread 72 modes per cavity simulated and measured modes in copper model with HOM absorbers 5 random seeds x 2 HOM orientations = 62 f HOM distributions no specific optimization of beam optics to maximize BBU threshold I=270 ma E. Pozdeyev
Qo Cavity tested vertically at Jlab and horizontally at BNL BNL1X with He vessel 1.00E+11 1.00E+10 Qo 1.00E+09 0 5 10 15 20 25 Eacc (MV/m)
Cavity in ERL enclosure Cornell style ferrite HOM damper
BNL-II New Cavity Design (R. Calaga) Reduce Hpeak by 18% to 4.7 mt/mv/m Increase Epeak 19% to 2.34 Increase R/Q 7% to 465Ω Reduce stiffness by a factor of 2. Apply new ideas in HOM damping: Reduce evanescent fundamental in beam tubes simplifies HOM probes Increase real-estate gradient Supported by a DOE HEP grant through Stony Brook CASE
Measurements on copper models (See Harald Hahn s presentation) In BNL I, damping is done with ferrites. For BNL II, we are considering pick-up probes in the beam tube. Measured Q HOM of a few 1000 s, Q FUND about 10 8. Expected result: Compact, simple HOM damping.
Field Normalized to Center Loop Magnets ERL 1.0000 Dipoles with vacuum chamber assembly Measurement setup Dipoles: 60 dipole chevron magnets, 20 cm bend angle Magnetic mapping done with rotating coil and Hall probe array. 1.0002 0.9998 0.9996 0.9994 0.9992 0.9990 0.9988 0.9986 0.9984 0.9982 0.9980 Dipole Measured and Calculated Radial Profiles Hall-1 Hall-2 Hall-3 Hall-3 Calculated -40-30 -20-10 0 10 20 30 40 50 Radial Position (mm) Measurements and simulations Quadrupoles: High field quality to preserve emittance. Emittance preservation verified by direct tracking of electrons. Dipole trim coil, can excite a sextupole component. W.Meng et al., Unique Features in Magnet Designs for R&D Energy Recovery Linac at BNL,PAC2007
Injection combined function magnets Very small real estate and large beam size: each magnet includes 4 sets of coils: 1) vertical bend, 2) quadrupole focusing, 3) sextupole correction and 4) horizontal steering. Window-frame dipole for Z-bend
RF 1 MW CW klystron 92kV at 17A 380 gpm of water
Klystron Transmitter System High Voltage PS and Transmitter The IGBT based power supply for the klystron is rated 100kV at 21A. This supply is part of the Continental Electronics transmitter which also supports the klystron with solenoid magnet power supplies, ion pump controllers, water monitoring, RF preamplification, RF forward and reflected power monitoring, and a PLC to perform these functions as well as control the high voltage power supply. 30
Main Dipole Power Supply Powers all six main dipoles in series. Magnet Power Supplies 320 Amps, 35 Volts, 100 ppm, Unipolar. Quadrupole, Solenoid, and Precision Steering Supplies 23 main quadrupoles, some small dipoles /solenoids. 10 Amps, 15 Volts, 100 ppm, Bipolar. 34 regulators required, six regulators per 19 inch rack. Precision Supplies for Special Series Magnets 20 Amps, 50 Volts, 100 ppm, Bipolar. One unit packaged in a 19 inch rack. Qty 5 power supplies required. Trim Power Supplies 4 Amps, 15 Volts, 1000 ppm, Qty 6 1 Amps, 10 Volts, 1000 ppm, Qty 32 31
Normilized emittance, mm*mrad Z-bend injection 45 40 35 30 25 20 15 10 5 0 0 200 400 600 800 e -, 4.7 MeV Z, cm vertical horizontal 48 cm 10º 20º e -, 18 MeV -20º e -, 30 MeV 54.3 MeV 1.5 SRF CELL Gun GUN MERGER 1 st 5 CELLS CAVITY -10º 490 cm
G5 Test Test of gun and 5-cell cavity at low power Characterize beam properties and injection
Schedule Gun cavity fabrication complete 9/09 Gun VTF testing 2/10 Hermetic String assembly 3/10 Injector cryomodule conditioning 5/10 Beam, no ERL (G5) 8/10 Full ERL Test 1/11