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

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 2015August 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

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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.

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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

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Charge exchange into synchrotron requires about 1014 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

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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.

Status Future

Intensity 78 mA (maximum)60 mA (accelerator study)33 mA (routine)

>60 mA (routine)

Pulse width/ duty factor 0.5 msec / 1.25 % 0.5 msec / 2.5 %

Pulse repetition rate 25 Hz 50 Hz (doubled for TEF*)

Emittance (RMS) 0.34 pmm.mrad (norm.) @ 66 mA

<0.30 pmm.mrad (norm.) @ 60 mA

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Hydrogen plasma produced by arc discharge interacts with a low work function Cs-Mo surface

Reliable, stable operation at 100 mA peak current, 400 ms pulse length, ~ 0.3 mm 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

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Magnetron H- source in operation: 80 mA peak current, 80 ms pulse width, 0.2 mm transverse emittance, duty factor: 0.4 % R&D GOALS:

1 year of continuous and stable operation

High brightness, low noise

Ion source for PIP-IIPIP-II: 800 MeV SRF LinacDC H- source with 5 – 10 mA current

Beam current stability (for frequencies > 1Hz i.e. ripples): ±0.5%600 ms 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 CsCapability to service the ion source with accelerator operating would be highly beneficial

Fermilab Ion Source, status and future requirements

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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 emA of U33/34+ or 2.8 x 1015 e/s

Leading approach: ECR Ion Source with high magnetic field has the required high ionization efficiencyNote: high intensity BNL EBIS can provide only about 5 x 1013 e/s

High intensity HI sources for heavy ion driver

1010

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 bathCold 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

Parameter Operations

Ion species O to U

Q/A 1/3 – 1/7

Beam intensity (eA, typical)

400

Energy (LEBT, keV/u) 12

Emittance (m, norm.99.5%)

0.9Z Q-ECR

I (emA)

Ip (pmA)

Argon 18 8 378 47.3

Calcium 20 11 468 42.5

Krypton 36 14 331 23.6

Xenon 54 18 334 18.5

Uranium 92 33, 34 438 13.1

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Generation of intense heavy ion beams: 55 mA (U4+) @ 131 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 ECRISHigh current of highly charged ions for Super-FRS for elements in the medium mass range A=80-150

GSI heavy ion sources – status and requirements

MeVVA higher repetition rate

Plasma Gabor lensPlasma Gabor lens

20 25 30 35 40 45 50

1

10

100

1000 28 GHz SC-ECRIS (extrapolated) 28 GHz SERSE 18 GHz SERSE 18 GHz RT-ECRIS 14 GHz GSI-CAPRICE II

inte

nsity

(eµ

A)

Xe charge state

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Beam-beam effects and IBS limit the brightness requirement for proton proton colliders to about 2 x 1011 protons per bunch with a transverse emittance of 1 - 2 mm.

Including losses and emittance growth during acceleration the requirement for the (polarized) H- source is therefore about 1 mm transverse emittance and about 0.5 mA peak current (in a 100 ms 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

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Original specification: 80 mA H- at 0.25 mm emittance in 400 ms (1 x 1014 protons per pulse)

HL-LHC needs only 3.5 x 1012 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 1013 ppp achievable by increasing pulselength (400 → 600 ms) or decreasing chopping factor orbuild a magnetron source(design ongoing, tests in July 15).

CERN – H- Ion Source for LHC-HL upgrade

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BNL - High intensity polarized H- source

Developed as BNL, TRIUMF, KEK, INR collaboration

1.0 mA in 300 ms (1.8 x 1012 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 1011 polarized protons

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Requirement limited by strong IBS in RHIC to 1-2 x 109 Au79+ per bunch with 2 mm transverse emittance

Full energy stochastic cooling to counteract IBS in RHIC allows for up to 3 x 109 Au79+ per bunch with 2 mm 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 108 Pb81+ per bunch with 1.2 mm transverse emittance

LHC Injector Upgrade goal: 1248 bunches with 1.2 x 108 Pb81+ per bunch with 0.9 mm 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

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RHIC first phase:Pulsed operation of Cs sputter source provides high intensity Au1- to Tandem

0.9 ms long pulse of heavy ion beam (Au31+ after stripping foil) from electrostatic Tandem with very low transverse emittance of 0.01 mm

Phase space painting during injection into AGS Booster synchrotron at 1 MeV/n; normalized transverse acceptance is about 1 mm

Rf capture and acceleration, stripping to Au77+ and a number of adiabatic bunch mergers: ~ 2 x 109 Au77+/bunch @ ~ 1 mm

Heavy ion bunches for RHIC

Target material

Cesium vapor feed

Cesium ionizer

Au¯

1717

RHIC second phase:Pulse of heavy ion beam (Au1+), 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 (Au32+) 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 109 Au77+/bunch @ ~ 1 mm

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

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Scheme to produce high intensity HI bunches for LHC:200 ms long pulse of heavy ion beam (Pb54+) 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 mm

Capture into 2 bunches and accelerate: ~ 3 x 108 Pb54+/bunch @ ~ 1 mm

Short lifetime of Pb54+ 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 Au32+ and SIS18 with U28+

Heavy ion bunches for LHC

Extraction@ 2880ms

35% loss at max. extracted intensity (5.5x108 Pb54+/bunch)

(Coasting beam)

B-field

RF capture

LIU Ions goal

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Center-of-mass energy range: 20 – 145 GeV

Full electron polarization at all energiesFull proton and 3He polarization at all energies

Need high brightness polarized 3He; unpolarized 3He has already been delivered from EBIS

Electron Ion Collider (EIC) – the next collider?

e-

p

80% polarized electrons:1.3 – 21.2 GeV

Polarized 3He 17 – 167 GeV/u

Light ions (d, Si, Cu)Heavy ions (Au, U)10 – 100 GeV/u

70% polarized protons 25 – 250 GeVLuminosity:

1033 – 1034 cm-2 s-1

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Two EIC designs

eRHIC at BNL MEIC at JLab

Warm ElectronCollider Ring(3 to 12 GeV)

Cold Ion Collider Ring(8 to 100 GeV)

IP IP

Electron Injector

12 GeV CEBAF

Ion SourceBooster Linac

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Optically pumped polarized 3He gas in high field EBIS solenoid

Feed into electron beam of EBIS for ionization to 3He2+ without depolarization: ~ 2 x 1011 polarized 3He2+ per bunch

High brightness polarized 3He source

3He+ Ionization to 3He++

Optical pumping inHigh magnetic field

5.0 T 5.0 T

Up to 2×1011

3He++ ions/pulse

J. Maxwell, C. Epstein, R. Milner, MITJ. Alessi, E. Beebe, A. Pikin, J. RitterA. Zelenski, BNL

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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 3He source

Summary