11 Brookhaven National Laboratory RHIC – Highly flexible and only US Hadron Collider NSLS II – One of the world's most advanced synchrotron light sources RHIC NSLS II AGS

2 ICIS 2015 August 23 – 28, 2015 Ion Source Requirements for High Energy Accelerators Thomas Roser BNL Particle physics experiments drive ion source development Source requirements for secondary beam production Source requirements for radioactive beam facilities Source requirements for colliders

33 Ion Sources, Accelerators and Particle Physics Progress in ion source and accelerator technology is motivated by and has driven advances in particle and nuclear physics This started with Ernest Lawrence’s first cyclotron (1931) and continues to this day.

44 Ion sources are instrumental to accelerator based Particle and Nuclear Physics Four main types of facilities: High intensity H- sources for proton drivers for secondary particle beam production (Kaon, muon neutrino beams) (J-PARC, Fermilab, CERN, …) High intensity heavy ion sources for HI drivers for radioactive beam production (RIKEN, GSI, FRIB, FAIR, …) High brightness (polarized) proton sources for proton-proton colliders (LHC, RHIC) High brightness heavy ion sources for heavy ion colliders (RHIC, LHC, NICA) Future requirements: Higher intensity H- beams (≥ 100 mA) for proton drivers Higher intensity of high charge state HI beams for RB facilities High intensity/brightness polarized H- beams for polarized proton colliders and polarized electron ion colliders Higher brightness high charge state heavy ion beams for HI colliders High brightness polarized deuteron and He-3 beams for electron ion collider Ion sources for particle physics

55 Charge exchange into synchrotron requires about proton per pulse. With about 200 turns and 1 micro-sec revolution time it needs about 100 mA peak current in the pulse Fewer turns will give less emittance growth and less losses but needs higher peak current High intensity H- sources for multi-GeV proton drivers

66 J-PARC Ion Source, status and future requirements A cesiated RF-driven negative hydrogen ion source was developed in a close collaboration between J-PARC and SNS. StatusFuture Intensity78 mA (maximum) 60 mA (accelerator study) 33 mA (routine) >60 mA (routine) Pulse width/ duty factor0.5 msec / 1.25 %0.5 msec / 2.5 % Pulse repetition rate25 Hz50 Hz (doubled for TEF*) Emittance (RMS) 0.34  mm.mrad 66 mA <0.30  mm.mrad 60 mA

77 Hydrogen plasma produced by arc discharge interacts with a low work function Cs-Mo surface Reliable, stable operation at 100 mA peak current, 400  s pulse length, ~ 0.3  m emittance for 6 months. Recently tested with 1 ms pulse and duty factor of 0.73% with capability to go to 1% with present cooling. Highest peak current H- source used at accelerators BNL Magnetron H- Source ~ 10 cm

88 Magnetron H- source in operation: 80 mA peak current, 80  s pulse width, 0.2  m transverse emittance, duty factor: 0.4 % R&D GOALS: 1 year of continuous and stable operation High brightness, low noise Ion source for PIP-II PIP-II: 800 MeV SRF Linac DC H- source with 5 – 10 mA current Beam current stability (for frequencies > 1Hz i.e. ripples): ±0.5% 600  s pulses for injection into Booster Transverse emittance: ~ 0.1 µm Mean time between maintenance (e.g.: filament replacement): > 350 hours Present limitation; would benefit greatly from longer lifetime PXIE: ion source from D-Pace, Inc. satisfies all requirements: Filament-driven, volume, no Cs Capability to service the ion source with accelerator operating would be highly beneficial Fermilab Ion Source, status and future requirements

99 Heavy ion drivers are used for the production of radioactive beams through fragmentation of the beam particles For cost effective, compact acceleration need high charge state from the source; for high beam power need high ionization efficiency Initial design for the next radioactive beam facility in the US called for 400 kW beam power with 400 MeV/n beam energy (RIA) Advances in source performance allowed for doubling of beam intensity to give the same beam power of 400 kW at 200 MeV/n and about half the facility cost! (FRIB) FRIB needs 440 e  A of U 33/34+ or 2.8 x e/s Leading approach: ECR Ion Source with high magnetic field has the required high ionization efficiency Note: high intensity BNL EBIS can provide only about 5 x e/s High intensity HI sources for heavy ion driver

10 Based on VENUS (LBNL) ECR Ion Source Design of solenoid/sextupole magnet employs radial-key-bladder design developed for high-field magnets (Berkeley, LARP) NbTi conductor, dry-wound, impregnated Magnet design modular. Coils can be swapped. Zero boil-off cryostat with LHe bath Cold mass cooled by 2 GM-JT cryo-coolers, boosting cooling capacity to 10 W Dual frequency RF power of10 kW (18 GHz + 28 GHz) FRIB heavy ion source ParameterOperations Ion speciesO to U Q/A1/3 – 1/7 Beam intensity (e  A, typical)400 Energy (LEBT, keV/u)12 Emittance (  m, norm.99.5%)0.9 ZQ-ECR I (e  A)I p (p  A) Argon Calcium Krypton Xenon Uranium9233,

11 Generation of intense heavy ion beams: 55 mA (U kV Transport of space charge dominated beams requires new LEBT concepts (plasma lens, halo collimation) with high level of space charge neutralization The future: 28 GHz ECRIS High current of highly charged ions for Super-FRS for elements in the medium mass range A= GSI heavy ion sources – status and requirements MeVVA  higher repetition rate Plasma Gabor lens

12 Beam-beam effects and IBS limit the brightness requirement for proton proton colliders to about 2 x protons per bunch with a transverse emittance of  m. Including losses and emittance growth during acceleration the requirement for the (polarized) H- source is therefore about 1  m transverse emittance and about 0.5 mA peak current (in a 100  s pulse) for one bunch. To support extensive halo scrapping (RHIC) or filling many more than a single bunch per source pulse (LHC) a substantially higher pulse current is required. LHC is planning to switch from proton to H- source to support LHC luminosity upgrade. Filling the large circumference of LHC with the high brightness beams requires a total current from the source that is similar to a proton driver. High brightness sources for proton-proton colliders

13 Original specification: 80 mA H- at 0.25  m emittance in 400  s (1 x protons per pulse) HL-LHC needs only 3.5 x protons per pulse, but smallest emittance. RF source (similar to SNS) to operate in surface mode with injection of Cesium Status: Test stand produces reliably 45 mA; emittance still slightly larger than RFQ acceptance (39 mA expected after the RFQ). HL-LHC beam intensity achievable, emittance being simulated. ISOLDE beam of 6.4 x ppp achievable by increasing pulse length (400 → 600  s) or decreasing chopping factor or build a magnetron source (design ongoing, tests in July 15). CERN – H- Ion Source for LHC-HL upgrade

14 BNL - High intensity polarized H- source Developed as BNL, TRIUMF, KEK, INR collaboration 1.0 mA in 300  s (1.8 x protons per pulse); 83% polarization One source pulse is captured and accelerated for one bunch in RHIC With inefficiencies and scraping to lower emittance and higher polarization bunch intensity in RHIC is 2.5 x polarized protons

15 Requirement limited by strong IBS in RHIC to 1-2 x 10 9 Au 79+ per bunch with 2  m transverse emittance Full energy stochastic cooling to counteract IBS in RHIC allows for up to 3 x 10 9 Au 79+ per bunch with 2  m transverse emittance at injection For LHC the requirement is limited by superconducting magnet quenches from collision products to 360 bunches per ring with 1.4 x 10 8 Pb 81+ per bunch with 1.2  m transverse emittance LHC Injector Upgrade goal: 1248 bunches with 1.2 x 10 8 Pb 81+ per bunch with 0.9  m transverse emittance For both RHIC and LHC no heavy ion source could deliver this required high brightness heavy ion beam directly High brightness source for heavy ion colliders

16 RHIC first phase: Pulsed operation of Cs sputter source provides high intensity Au 1- to Tandem 0.9 ms long pulse of heavy ion beam (Au 31+ after stripping foil) from electrostatic Tandem with very low transverse emittance of 0.01  m Phase space painting during injection into AGS Booster synchrotron at 1 MeV/n; normalized transverse acceptance is about 1  m Rf capture and acceleration, stripping to Au 77+ and a number of adiabatic bunch mergers: ~ 2 x 10 9 Au 77+ ~ 1  m Heavy ion bunches for RHIC Target material Cesium vapor feed Cesium ionizer Au¯

17 RHIC second phase: Pulse of heavy ion beam (Au 1+ ), from hollow cathode or laser ion source, injected into Electron Beam Ion Source (EBIS) used as charge neutralized ion accumulator and charge breeder. Reach average charge state (Au 32+ ) after about 40 ms. Extract short pulse of heavy ion beam and accelerate in IH Linac to 2 MeV/n 2 turn injection into AGS Booster synchrotron; Rf capture and acceleration Multiple Booster cycles and adiabatic bunch mergers: ~ 3 x 10 9 Au 77+ ~ 1  m Heavy ion bunches for RHIC (cont’d) Hollow Cathode Ion Source for injection of 1+ ions into EBIS Laser Ion Source for injection of 1+ ions into EBIS

18 Scheme to produce high intensity HI bunches for LHC: 200  s long pulse of heavy ion beam (Pb 54+ ) from ECRIS in afterglow mode and accelerated in IH Linac to 4.2 MEV/n Phase space painting injection of multiple pulses into Low Energy Ion Ring (LEIR) with fast electron cooling during injection, stack cooled to 0.7  m Capture into 2 bunches and accelerate: ~ 3 x 10 8 Pb 54+ ~ 1  m Short lifetime of Pb 54+ ions in LEIR due to well known charge-exchange loss from residual gas desorbed from walls of vacuum chamber. Also observed at AGS Booster with Au 32+ and SIS18 with U 28+ Heavy ion bunches for LHC 2880ms 35% loss at max. extracted intensity (5.5x10 8 Pb 54+ /bunch) (Coasting beam) B-field RF capture LIU Ions goal

19 Center-of-mass energy range: 20 – 145 GeV Full electron polarization at all energies Full proton and 3 He polarization at all energies Need high brightness polarized 3 He; unpolarized 3 He has already been delivered from EBIS Electron Ion Collider (EIC) – the next collider? e-e- p 80% polarized electrons: 1.3 – 21.2 GeV Polarized 3 He 17 – 167 GeV/u Light ions (d, Si, Cu) Heavy ions (Au, U) 10 – 100 GeV/u 70% polarized protons 25 – 250 GeV Luminosity: – cm -2 s -1

20 Two EIC designs eRHIC at BNLMEIC at JLab Warm Electron Collider Ring (3 to 12 GeV) Cold Ion Collider Ring (8 to 100 GeV) IP Electron Injector 12 GeV CEBAF Ion Source Booster Linac

21 Optically pumped polarized 3 He gas in high field EBIS solenoid Feed into electron beam of EBIS for ionization to 3 He 2+ without depolarization: ~ 2 x polarized 3 He 2+ per bunch High brightness polarized 3 He source 3 He + Ionization to 3 He ++ Optical pumping in High magnetic field 5.0 T Up to 2× He ++ ions/pulse J. Maxwell, C. Epstein, R. Milner, MIT J. Alessi, E. Beebe, A. Pikin, J. Ritter A. Zelenski, BNL

22 Progress in ion source technologies has driven performance of accelerators in particle and nuclear physics Planned upgrades and future machines need further ion source improvements: higher intensity, higher brightness, higher polarization as well as a new source: high brightness polarized 3 He source Summary