W HAT A BOUT THE F RONT E ND ? 30 October 2010, Osaka Ciprian - PowerPoint PPT Presentation

W HAT A BOUT THE F RONT E ND ? 30 October 2010, Osaka Ciprian Plostinar

W IKI W ARS

H IGH I NTENSITY , H IGH P OWER  Growing interest for high power proton accelerators (MW range beams)  Drivers for spallation neutron sources  Production of radioactive beams for nuclear physics  Nuclear Reactors  Transmutation of Nuclear Waste  Neutrino Factories for Nuclear Physics  Etc...

ISIS

SNS

J-PARC

P ROJECTS W ORLDWIDE by courtesy of C. Prior

H IGH I NTENSITY , H IGH P OWER  Typical HPPA Layout: RING ¡ Front ¡End ¡ Linac ¡(NC/SC) ¡ 66 cells  A proposed 50 Hz, 4 MW, 10 GeV 3 GeV RCS booster proton driver for the Neutrino 10 GeV Factory based on a non-scaling H°, H¯ non-scaling FFAG FFAG 180 MeV H¯ linac H¯ collimators

T HE F RONT E ND Ion ¡Source ¡ LEBT ¡ RFQ ¡ MEBT ¡ A few MeV High Current Operation High duty cycle  For MW operation significant technical development is necessary.  The Front End could be one of the bottlenecks in the acceleration chain. T HE F RONT E ND T EST S TAND @ RAL RFQ MEBT LEBT H- Ion source

The Front End Test Stand @ RAL RFQ MEBT LEBT H- Ion source MEBT and chopper Magnetic LEBT RFQ Laser profile monitor H − ion source

T HE F RONT E ND T EST S TAND @ RAL - T HE I ON S OURCE - F IRST FETS B EAM , A PRIL 2009 35 mA H - , 200 µ s, 50 Hz L ATEST BEAM CURRENT MEASUREMENTS 70 mA H - , 1 ms, 50 Hz

T HE F RONT E ND T EST S TAND @ RAL - T HE I ON S OURCE - Beam Parameter ISIS Ion Source (presently) FETS Ion Source Total Energy 35 keV 65 keV Current 55 mA (but only 35 mA to 60 – 70 mA LEBT!) Rep. Rate 50 Hz 50 Hz Pulse Length 200 μ s 2 ms Normalised x emittance 0.9 π mm mRad 0.3 π mm mRad Normalised y emittance 0.8 π mm mRad 0.3 π mm mRad Summary of Main Design Improvements Duty Cycle/Cooling Extraction Discharge Current Sector Magnet Poles Permanent Magnet Penning Field Postacceleration

T HE F RONT E ND T EST S TAND @ RAL - T HE L OW E NERGY B EAM T RANSPORT L INE -  Beam must be focussed from >20mm at Ion Source to 2-3mm at RFQ.  Large dynamic range required to handle beam size and space charge.  3 solenoid design provides effective focussing with minimal emittance growth. Transmission Measurement Simulation

T HE F RONT E ND T EST S TAND @ RAL - T HE RFQ - I NTEGRATED D ESIGN CAD Model CST Field Model Beam • CAD package produces accurate model of vane tips. � Dynamics • Electrostatic field model in Simulation CST. � s • Beam dynamics simulations in GPT. � • Good agreement between this method and RFQSIM model for 4-rod and 4-vane. � • Need to optimise RFQ design to increase acceptance. � 14 �

T HE F RONT E ND T EST S TAND @ RAL - T HE MEBT C HOPPER L INE -

T HE F RONT E ND T EST S TAND @ RAL - T HE MEBT C HOPPER L INE -  CERN Linac4 MEBT  J-PARC MEBT  SNS MEBT

T HE F RONT E ND T EST S TAND @ RAL - T HE C HOPPING P RINCIPLE ?  The Beam Chopper  Produces gaps in the bunched beam  Enables low beam loss operation during injection in accumulator rings  Low energy (2.5 – 3 MeV ), high duty cycle (~1-10%) beam chopping has not been demonstrated yet. Ring RF buckets at low frequency (a few MHz) Linac bunches at high frequency (324 MHz) Lost/partially lost linac bunches

T HE F RONT E ND T EST S TAND @ RAL T HE F AST -S LOW C HOPPING S CHEME To achieve perfect chopping a very Fast-Slow Chopping Scheme high speed (<2 ns) chopper is required

T HE F RONT E ND T EST S TAND @ RAL - T HE C URRENT MEBT S CHEME - • Two opposing requirements: Elem. Type No Length Prop. Quadrupoles 11 70 mm G = 9 - 33 T/ Provide strong transverse 1. m focusing Buncher 4 200 mm V = 75 – 100 Cavities kV Provide sufficiently long 2. Fast Chopper 1 450 mm V = +/- 1.3 kV empty drifts for the choppers Slow Chopper 1 450 mm V= +/- 1.5 kV Beam Dumps 2 400 mm -

T HE F RONT E ND T EST S TAND @ RAL - T HE C URRENT MEBT S CHEME - Beam Envelopes Slow Chopper Fast Chopper 23.2 mm centre separation 21.8 mm centre separation 4.5 mm gap between the 99% emit ellipses. 2.6 mm gap between the 99% emit ellipses.

T HE F RONT E ND T EST S TAND @ RAL - T HE C URRENT MEBT S CHEME - Chopper Electrode Design Short length helical prototype Short length planar prototype Hybrid Quadrupoles Re-bunching cavities

A LTERNATIVE MEBT D ESIGN RFQ MEBT DTL ?  RFQ, DTL – focusing elements adjusted -> smooth beam phase advances  FODO structure – high quality beam transport if the zero current phase advance/period < 90 ° (envelope stability criteria) Q C Q CHOPPER Q Q Q C Q CHOPPER Q Q Q C Q

MEBT D ESIGN C ONSIDERATIONS  New MEBT Optics  Regular lattice between the RFQ and the DTL (strong focusing, smooth phase advance variation - FODO).  Multiple short beam choppers.  The choppers can’t be placed anywhere, but at positions where the kicks will add up.  For a 90° phase adv/cell (FODO) the kickers should be placed in every other cell.  Chopping in both planes (vertical & horizontal).  Deflecting alternatively up and down (left - right).  One can make the MEBT as long as necessary to get the required deflection.

FODO L ATTICE (P RELIMINARY ) – C HOPPERS OFF

FODO L ATTICE – F AST C HOPPER ON

FODO L ATTICE – S LOW C HOPPER ON

FODO L ATTICE – B OTH C HOPPERS ON

FODO L ATTICE – B OTH C HOPPERS ON

FODO L ATTICE FODO: Chopped beam by the FODO MEBT - Emittance Evolution slow chopper(%) 0.50 Emittance (Pi.mm.mrad) 100.00 0.45 80.00 0.40 60.00 0.35 % 40.00 Et 20.00 0.30 Ez 0.00 0.25 0.00 2.00 4.00 6.00 8.00 -20.00 0.20 Position (m) 0.00 2.00 4.00 6.00 8.00  Advantages Position (m)  Small emittance growth  Zero Losses  No partially chopped beam  ~20% less voltage required on the chopper plates in current configuration (coverage factor not taken into account)  Chopped beam distributed on several beam dumps  Easier DTL matching  Can add more cells if required, to reduce the voltage

FFDD L ATTICE (P RELIMINARY ) – C HOPPERS OFF

FFDD L ATTICE – F AST C HOPPER ON

FFDD L ATTICE – S LOW C HOPPER ON

FFDD L ATTICE – B OTH C HOPPERS ON

FFDD L ATTICE – B OTH C HOPPERS ON

FFDD L ATTICE FFDD: Chopped beam by the FFDD MEBT - Emittance Evolution slow chopper(%) 0.50 Emittance (Pi.mm.mrad) 100.00 0.45 80.00 0.40 60.00 0.35 % 40.00 Et 0.30 20.00 Ez 0.25 0.00 0.20 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 -20.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 Position (m) Position (m)  Advantages Similar to FODO +  Fewer chopper plates than FODO  Less voltages required 

C OMPARISON WITH E XISTING DESIGNS  FETS MEBT  Solenoid MEBT FETS MEBT - Emittance Evolution Solenoid MEBT - Emittance Evolution 0.50 Emittance (Pi.mm.mrad) Emittance (Pi.mm.mrad) 0.45 0.50 0.45 0.40 0.40 0.35 0.35 Et 0.30 Et 0.30 Ez 0.25 0.25 Ez 0.20 0.20 0.00 1.00 2.00 3.00 4.00 5.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Position (m) Position (m)

MEBT + DTL E MITTANCE E VOLUTION MEBT + DTL Emittance Evolution 0.50 0.45 Emittance (Pi.mm.mrad) 0.40 Et - FFDD Ez - FFDD 0.35 Et - FODO Ez - FODO Et - Solenoid 0.30 Ez - Solenoid Et - FETS 0.25 Ez - FETS 0.20 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 0.15 Position (m)

C ONCLUSIONS  Front End Test Stand at RAL is progressing well  Ion Source and LEBT installed  New RFQ design approach  Innovative MEBT optics under consideration  Comprehensive diagnostics currently being developed and tested