m. a. clarke-gayther ral/fets/hippi uk-nf 16 th september 2008 beam chopper development for next...
TRANSCRIPT
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Beam Chopper Development for
Next GenerationHigh Power Proton Drivers
Michael A. Clarke-GaytherRAL / FETS / HIPPI
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Overview
Fast Pulse Generator (FPG)
Slow Pulse Generator (SPG)
Slow – wave electrode designs
Summary
Outline
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Maurizio Vretenar(HIPPI WP coordinator)Alessandra Lombardi(WP4 Coordinator)Luca Bruno, Fritz CaspersFrank Gerigk, Tom KroyerMauro PaoluzziEdgar Sargsyan, Carlo Rossi
Mike Clarke-Gayther (WP4 Fast Beam Chopper & MEBT)
Chris Prior (WP coordinator) Ciprian Plostinar (WP2 & 4 N-C Structures / MEBT)Christoph Gabor (WP5 / Beam Dynamics)
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
John Back (LEBT)
Saad Alsari (RF)Simon Jolly, Ajit Kurup (RFQ)David Lee (Laser Diagnostics) Jaroslav Pasternack (UK-NF)Jürgen Pozimski (Ion source/ RFQ)Peter Savage (Mechanical Eng.)
Mike Clarke-Gayther (Chopper / MEBT)Dan Faircloth, Scott Lawrie (Ion source)Alan Letchford (RFQ / FETS coordinator)Mike Perkins (Ion source power supplies)Jürgen Pozimski (Ion source / RFQ)Pierpaolo Romano (Beam stop) Philip Wise (Mechanical Eng.)
Christoph Gabor(Diagnostics)Ciprian Plostinar (MEBT / DTL) Javier Bermejo (ESS)
Jesus Alonso (ESS)Rafael Enparantza (ESS)
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
A Fast Beam chopper for
Next Generation Proton Drivers (NGPDs) / Motivation
Key enabling component for all NG synchrotron and accumulator ring based proton drivers
• Beam loss during trapping is a ‘show stopper’
• Order of magnitude reduction in loss required to supportoperating regime of ‘hands on maintenance’ (1W/m)
• All existing NGPDs have suboptimal chopper designs
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
A Fast Beam chopper for
Next Generation Proton Drivers (NGPDs) / Motivation
FETS will test a unique, UK designed, fast beam chopper with the potential to be the first to demonstrate efficient operation on ring based NGPDs for spallation neutron sources and neutrino factories
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
A Fast Beam chopper for
Next Generation Proton Drivers / Motivation
To significantly reduce beam loss at trapping / extraction• Enables ‘Hands on’ maintenance (1 Watt / m)
To support complex beam delivery schemes• Enables low loss ‘switchyards’ and duty cycle control
To provide beam diagnostic function• Enables low duty cycle (i.e. ‘low risk)’ accelerator tuning
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Design Project Position Type Chopping Status
RALESS & FETS
MEBTSlow-wave
& ArrayUni-
directionalPrototype
CERN SPL MEBT Slow-waveUni-
directionalAdvanced prototype
LANL/LBNL SNSMEBT
& LEBT
Slow-wave
& DiscreteUni & quad
Installed
& tested
JAERI JPARCMEBT
& LEBT
Cavity &
Induction
Bi &
Longitudinal
Installed
& tested?
FNAL ‘X’ MEBT Slow-wave Uni Prototype
Fast beam chopper schemes
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
The RAL Front-End Test Stand (FETS) Project / Key parameters
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
RAL ‘Fast-Slow’ two stage chopping scheme
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
3.0 MeV MEBT Chopper (RAL FETS Scheme A)
Chopper 1 (fast transition)
Chopper 2 (slower transition)
‘CCL’ type re-buncher cavities
4.8 m
Beam dump 1
Beam dump 2
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
3.0 MeV MEBT Chopper (RAL FETS Scheme A)
Chopper 1 (fast transition)
‘CCL’ type re-buncher cavities
2.4 m
Beam dump 1 (low duty cycle)
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
3.0 MeV MEBT Chopper (RAL FETS Scheme A)
Chopper 2 (slower transition)
‘CCL’ type re-buncher cavities
2.4 m
Beam dump 2(high duty cycle)
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
FETS Scheme A / Beam-line layout and GPT trajectory plots
Losses:0.1 % @ input to CH1, 0.3% on dump 10.1% on CH2, 0.3% on dump 2
Voltages:Chop 1: +/- 1.28 kV (20 mm gap)Chop 2: +/- 1.42 kV (18 mm gap)
Overview
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
KEY PARAMETERS SCHEME A
ION SPECIES H-
ENERGY (MeV) 3.0
RF FREQUENCY (MHz) 324
BEAM CURRENT (mA) 40 - 60
NORMALISED RMS INPUT EMITTANCE IN X / Y / Z PLANES
( π.mm.mr & π.deg.MeV)
0.25 / 0.25 / 0.18
RMS EMITTANCE GROWTH IN X / Y / Z PLANES (%) 6 / 13 / 2
CHOPPING FACTOR (%) 30 - 100
CHOPPING EFFICIENCY (%) 99.9
FAST CHOPPER PULSE: TRANSITION TIME / DURATION / PRF/ BURST DURATION / BRF
2 ns / 12 ns / 2.6 MHz / 0.3 – 2 ms / 50 Hz
FAST CHOPPER ELECTRODE EFFECTIVE LENGTH / GAPS (mm) 450 x 0.82 = 369 / 20
FAST CHOPPER POTENTIAL(kV) ± 1.3
SLOW CHOPPER PULSE: TRANSITION TIME / DURATION /
PRF/ BURST DURATION /
BRF
12 ns / 250 ns – 0.1 ms 1.3 MHz / 0.3 – 2 ms /
50 Hz
SLOW CHOPPER EFFECTIVE LENGTH / GAPS (mm) 450 x 0.85 / 18
SLOW CHOPPER POTENTIAL (kV) ± 1.5
POWER ON FAST / SLOW BEAM DUMPS (W) 150 / 850
OPTICAL DESIGN CODE(S) IMPACT / TRACEWIN
/ GPT
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Open animated GIF in Internet Explorer
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Fast Pulse Generator (FPG) development
FPG development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
9 x Pulse generator cards
High peak power loads
Control and interface
Combiner
9 x Pulse generator cards
Power supply
9 x Pulse generator cards
9 x Pulse generator cards
1.7 m
FPG / Front View
FPG development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Pulse Parameter FETS Requirement Measured Compliancy Comment Amplitude (kV into 50 Ohms) ± 1.4 ± 1.5 Yes Scalable Transition time (ns) ≤ 2.0 Trise = 1.8, Tfall = 1.2 Yes 10 – 90 % Duration (ns) 10 - 15 10 - 15 Yes FWHM Droop (%) 2.0 in 10 ns 1.9 in 10 ns Yes F3dB ~ 300 kHz Repetition frequency (MHz) 2.4 2.4 Yes Burst duration (ms) 0.3-1.5 1.5 Yes Burst repetition frequency (Hz) 50 50 Yes Duty cycle ~ 0.27 % Post pulse aberration (%) ± 2 ± 5 No Reducible Timing stability (ps over 1 hour) ± 100 ± 50 Yes Peak to Peak Burst amplitude stability (%) + 10, - 5 + 5, - 3 Yes
FPG waveform measurement
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Slow Pulse Generator (SPG) development
M. A. Clarke-Gayther RAL/FETS/HIPPI
SPG development
UK-NF 16th September 2008
16 close coupled ‘slow’ pulse generator modules
Slow chopperelectrodes
Beam
SPG beam line layout and load analysis
M. A. Clarke-Gayther RAL/FETS/HIPPI
SPG development
UK-NF 16th September 2008
Prototype 8 kV SPG euro-cassette module / Side view
Low-inductance HV damping resistors
8 kV push-pull MOSFET switch module
High voltagefeed-through(output port)
Axial cooling fans
Air duct
0.26 m
M. A. Clarke-Gayther RAL/FETS/HIPPI
SPG development
UK-NF 16th September 2008
SPG waveforms at ± 4 kV peak & 50 ns / div.
SPG waveform measurement / HTS 41-06-GSM-CF-HFB (4 kV)
SPG waveforms at ± 4 kV peak & 0.2 ms / div.
Pulse Parameter FETS Requirement Measured Compliancy Comment
Amplitude (kV into 50 Ohms) ± 1.5 ± 4.0 Yes ± 4 kV rated
Transition time (ns) ~ 12.0 Trise ~ 12, Tfall ~ 11 Yes 500 pulses
Duration (μs) 0.23 – 100 0.17 – 100 Yes FWHM
Droop (%) 0 0 Yes DC coupled
Repetition frequency (MHz) 1.3 1.3 Yes
Burst duration @ 1.3 MHz 0.3 – 1.5 ms 1 ms Close Limited by cooling
Burst repetition frequency (Hz) 50 25 Close Limited by cooling
Post pulse aberration (%) ± 5 ≤ ± 5 Yes Damping dependent
Pulse width stability (ns) ± 0.1 8.2 ns (n=1 to 2) Limited Can be corrected
Timing stability (ns over 1 hour) ± 0.5 ± 0.3 Yes Over temperature
Burst amplitude stability (%) + 10, - 5 < + 10, -5 Yes Limited by power reg.
Tr =11.3 ns
Tf =11.3 ns
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Where:
Transverse extent of the beam: L2Beam transit time for distance L1: T(L1) Pulse transit time in vacuum for distance L2: T(L2) Pulse transit time in dielectric for distance L3: T(L3) Electrode width: L4
For the generalised slow wave structure:Maximum value for L1 = V1 (T3 - T1) / 2Minimum Value for L1 = L2 (V1/ V2)T(L1) = L1/V1 = T(L2) + T(L3)
The relationships for field (E), and transverse displacement (x), where q is the electronic charge, is the beam velocity, m0 is the rest mass, z is the effective electrode length, is the
required deflection angle, V is the deflecting potential, and d is the electrode gap, are:
zqmE
2
0tan
d
VE 2
0
2
2
m
zEqx
‘E-field chopping / Slow-wave electrode design
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
‘On-axis field in x, y plane
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Preliminary test assemblies
Coaxial Helical Planar
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Preliminary test assemblies
The manufacture and test of these preliminary assemblies will provide important information on the following: Construction techniques. NC machining and tolerances.Selection of machine-able ceramics and of suitable copper and aluminium alloys. Electroplating and electro-polishing. Accuracy of the 3D high frequency design code.
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Coaxial test assembly / Shapal-M version
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Helical test assembly
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Helical B2 / Short length prototype
UT-390 semi-rigidcoaxial delay lines
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Helical B2 / CAD view
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
RAL Planar / Short length prototype
Slow-wave electrode development
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
RAL Planar / Short length prototype
Summary
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
FPG• Meets key specifications
SPG• 4 kV version looks promising
Slow-wave electrode designs• Measurements on coaxial test assembly have:
• Verified accuracy of high frequency modelling code• Tested effect of mechanical tolerances • Tested machining properties of selected ceramic material
• Measurements on helical test assembly have:• Tested effect of strip-line tolerances and electro-polishing• Probed limitations of NC machining practice
Summary
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
Slow-wave electrode designs (continued):
• Planar test assembly – design in progress – to test:• Machining properties of ceramic support pillars• Strip-line clamping and positioning tolerances
The design and manufacture of the subsequent planar and helical ‘short length’ prototype structures, will build on the experience gained from the preliminary test assemblies, and should facilitate the choice of a candidate design for the full scale structure.
References
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
HIPPI WP4: The RAL† Fast Beam Chopper Development Programme Progress Report for the period: January 2007 – June 2008
M. A. Clarke-Gayther
STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK
EU contract number RII3-CT-2003-506395 CARE-Report-08-016-HIPPI
References
M. A. Clarke-Gayther RAL/FETS/HIPPI UK-NF 16th September 2008
M Clarke-Gayther, ‘The development of a fast beam chopper for next generation high power proton drivers’, Proc. of EPAC 2008, Genoa, Italy, 23rd – 27th June, 2008, pp. 3584-3586.
M Clarke-Gayther, ‘Slow-wave chopper structures for next generation high power proton drivers’, Proc. of PAC 2007, Albuquerque, New Mexico, USA, 25th – 29th June, 2007, pp. 1637-1639
M Clarke-Gayther, G Bellodi, F Gerigk, ‘A fast beam chopper for the RAL Front-End Test Stand’, Proc. of EPAC 2006, Edinburgh, Scotland, UK, 26th - 30th June, 2006, pp. 300-302.
M Clarke-Gayther, ‘Fast-slow beam chopping for next generation high power proton drivers’, Proc. of PAC 2005, Knoxville, Tennessee, USA, 16th – 20th May, 2005, pp. 3637-3639
M Clarke-Gayther, ‘A fast beam chopper for next generation proton drivers’, Proc. of EPAC 2004, Lucerne, Switzerland, 5th – 9th July, 2004, pp. 1449-1451
M Clarke-Gayther, ‘Slow-wave electrode structures for the ESS 2.5 MeV fast chopper’, Proc. of PAC 2003, Portland, Oregon, USA, 12th - 16th May, 2003, pp. 1473-1475
F Caspers, ‘Review of Fast Beam Chopping’, Proc. of LINAC 2004, Lubeck, Germany, 16 th – 20th August, 2004, pp. 294-296.
F Caspers, A Mostacci, S Kurennoy, ‘Fast Chopper Structure for the CERN SPL’, Proc. of EPAC 2002, Paris, France, 3rd – 7th June, 2002, pp. 873-875.