Beam Chopper R

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Beam Chopper R D forNext GenerationHigh
Power Proton Drivers
Michael A. Clarke-Gayther
RAL / ASTeC / HIPPI
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Project planning / Overview
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Project planning / Detail
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EU contract number RII3-CT-2003-506395 CARE/HIPPI Document-2005-008
HIPPI WP4 The RAL Fast Beam Chopper Development
Programme Progress Report for the period
January 2004 June 2005 M. A. Clarke-Gayther
CCLRC Rutherford Appleton Laboratory,
Didcot, Oxfordshire, UK
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Outline
See Giulia Bellodis talk later in this
session

• Fast Slow chopping
• RAL Front-End Test Stand (FETS) chopping schemes
• High voltage pulse generator development
• Fast Pulse Generator (FPG)
• Slow Pulse Generator (SPG)
• Slow wave structure development
• Helical structure B
• Helical structure C

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Fast Slow chopping
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Fast and slowchoppermodules
Chopper 1 (fast transition)
BEAM
Chopper 2 / Beam dump(slower transition)
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RAL FETS chopping schemes
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KEY PARAMETERS SCHEME A (FETS) SCHEME B (FETS) SCHEME C (ESS)
ION SPECIES H- H- H-
ENERGY (MeV) 3.0 3.0 2.5
RF FREQUENCY (MHz) 324 324 280
BEAM CURRENT (mA) 57 57 57
NORMALISED RMS INPUT EMITTANCE IN X / Y / Z PLANES ( p.mm.mr p.deg.MeV) 0.25 / 0.25 / 0.18 0.25 / 0.25 / 0.18 0.2 / 0.2 / 0.13
RMS EMITTANCE GROWTH IN X / Y / Z PLANES () 12 / 16 / 4 27 / 27 / - 3 12 / 12 / - 5
CHOPPING FACTOR () 30 30 30 - 100
CHOPPING EFFICIENCY () 99.5 99.7 100
FAST CHOPPER PULSE TRANSITION TIME / DURATION / PRF/ BURST DURATION / BRF 2 ns / 9 ns / 2.6 MHz / 0.3 µs / 50 Hz 2 ns / 9 ns / 2.6 MHz / 0.3 µs / 50 Hz 2 ns / 12 ns / 2.4 MHz / 1 ms / 50 Hz
FAST CHOPPER ELECTRODE EFFECTIVE LENGTH / GAPS (mm) 500 / 20 500 / 20 (340 x 0.73 248) / 14
FAST CHOPPER POTENTIAL (V) 2000 1500 2200
SLOW CHOPPER PULSE TRANSITION TIME / DURATION / PRF/ BURST DURATION / BRF 9 ns / 0.1 µs / 1.3 MHz / 0.3 µs / 50 Hz 9 ns / 0.1 µs / 1.3 MHz / 0.3 µs / 50 Hz 12 ns / 240 ns 0.1 ms / 1.2 MHz / 1 ms / 50 Hz
SLOW CHOPPER EFFECTIVE LENGTH / GAPS (mm) 500 / 20 500 / 20 (360 x 0.8 288) / 11
SLOW CHOPPER POTENTIAL (V) 2000 3000 6000
POWER ON FAST / SLOW BEAM DUMPS (W) 150 / 850 150 / 850 1250 x 4
OPTICAL DESIGN CODES IMPACT / PATH IMPACT / PATH PARMILA / TRACE GPT
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Fast Pulse Generator (FPG) Development
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Phase 1 FPG system Single polarity _at_ 1.4 kV max.
High peak power load
Control and interface
Combiner
9 x Pulse generator cards
9 x Pulse generator cards
Power supply
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M. A. Clarke-Gayther
RAL/ASTeC/HIPPI
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Phase 2 FPG system Dual polarity _at_ 1.4 kV max.
High peak power loads
Control and interface
Power supply
9 x Pulse generator cards
9 x Pulse generator cards
Combiner
9 x Pulse generator cards
9 x Pulse generator cards
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M. A. Clarke-Gayther
RAL/ASTeC/HIPPI
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Phase 2 FPG waveform measurement
FPG Waveforms at 1.4 kV peak 2 µs / div.
FPG Waveforms at 1.4 kV peak 5 ns / div.
FPG Waveforms at 1.4 kV peak 100 ns / div.
FPG Waveforms at 1.4 kV peak 0. 2 ms / div.
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Phase 2 FPG waveform measurement
FPG timing jitter at 10 ps / div.
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Measured performance parameters for the Phase 2
FPG system
Pulse Parameter ESS Requirement Measured Compliancy Comment
Amplitude (kV into 50 Ohms) 2.2 1.5 No 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) 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
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Time amplitude dependent FPG waveform analysis
/ 324 MHz FETS scheme
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FPG duty cycle and LF droop for the ESS and FETS
schemes
Assumes 4 kV SPG with 9 ns transition time
(10 90 ) Assumes 8 kV SPG with 12 ns
transition time (10 90)
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FPG duty cycle droop compensation
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FPG duty cycle droop compensation
I.S. RAMPING (100 CHOPPING)
30 CHOPPING
OFF
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FPG duty cycle droop compensation
I.S. RAMPING (100 CHOPPING)
30 CHOPPING
OFF
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FPG duty cycle droop compensation
I.S. RAMPING (100 CHOPPING)
30 CHOPPING
OFF
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FPG duty cycle droop compensation
CH
BEAM
I.S. RAMPING
CH
BEAM
CH
BEAM
CH
BEAM
CH
805 ns
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FPG duty cycle droop compensation
CH
BEAM
I.S. RAMPING
CH
BEAM
CH
BEAM
CH
BEAM
CH
805 ns
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Slow Pulse Generator (SPG) Development
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SPG beam line layout and load analysis
Slow chopper electrodes
Beam
16 close coupled slow pulse generator modules
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SPG prototype system / Electronic implementation
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SPG prototype system / Modular construction
SPG Module
0.8 m
0.28 m
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Prototype SPG module / Side view
Axial cooling fans
Air duct
0.26 m
Non-inductive damping resistors
8 kV push-pull MOSFET switch module
High voltage feed-through (output port)
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SPG pre-prototype Breadboard system
- 8 kV 5 µF LF cap.bank
8 kV 5 µF LF cap.bank
- 8 kV 3 nF HF cap.bank
8 kV 3 nF HF cap.bank
HVdamping resistor
8 kV push-pullMOSFETswitch
Two turn load inductance 50 nH
Load capacitance 30 pf
6 kV, 400 MHz 1000 probe
Trigger input
Auxiliary power supplies
Cooling fan
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Breadboard SPG waveform measurement
SPG waveforms at 6 kV peak 50 ns / div.
SPG waveforms at 6 kV peak 0.2 ms / div.
SPG waveforms at 6 kV peak 0.5 µs / div.
SPG timing jitter at 100ps / div.
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Measured performance parameters for the
Breadboard SPG system
Pulse Parameter ESS Requirement Measured Compliancy Comment
Amplitude (kV into 50 Ohms) 6.0 6.0 Yes 8 kV rated
Transition time (ns) 12.0 Trise 13, Tfall 12 Yes 10 90
Duration (µs) 0.2 100 0.2 100 Yes FWHM
Droop () 0 0 Yes DC coupled
Repetition frequency (MHz) 1.2 1.2 ( 6 µs burst) Limited Burst limitation
Burst duration _at_ 1.2 MHz 1.5 ms 6 µs No Burst limitation
Burst duration _at_ 0.1 MHz PRF - 10 ms - PRF limitation
Burst repetition frequency (Hz) 50 50 Yes Duty cycle 0.27
Post pulse aberration () 2 2 Yes
Timing stability (ns over 1 hour) 0.5 0.4 Yes Peak to Peak
Burst amplitude stability () 10, - 5 lt 10, -5 Limited _at_ 0.1 MHz PRF
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Slow Wave structure Development
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Helical structure B with L - C trimmers and
adjustable delay
Adjustable L-C trimmer
Adjust cable lengths to change delay
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Helical structure C with L - C trimmers
Quadrupole bore diameter
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• Summary
• Three candidate chopping schemes for RAL FETS
• Schemes A B ready for first engineering
  analysis
• FPG can meet ESS and RAL FETS requirements
• Duty cycle droop compensation scheme to be
  tested
• SPG prototype system designed and part
  constructed
• Pre - prototype measurements show PRF limitation
• Slow wave structure engineering concepts
  refined
• L C impedance trimming and adjustable delay
  

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Fast-Slow Beam Chopping for next generation
high power proton drivers,M.A. Clarke-Gayther,
Proc. of PAC 2005, Knoxville, Tennessee, USA,
16-20 May, 2005, at press.CARE-Conf-05-015-HIPPI
Re-design of the RAL chopper line F Gerigk, G
Bellodi CCLRC, ASTeC, Intense Beams
Group HIPPI-WP5 meeting, Coseners House,
Abingdon, UK 13th April 2005 http//gerigk.home.ce
rn.ch/gerigk/talks/hippi_ral_bd_0405.pdf A fast
beam chopper for next generation high power
proton drivers,M. A. Clarke-Gayther, Proc. of
the Ninth EPAC, Lucerne, Switzerland, 5-9 July,
2004, p. 1449-1451CARE-Conf-04-009-HIPPI A
new 180 MeV H- Linac for Upgrades of ISIS, F.
Gerigk Proc. of the ninth EPAC, Lucerne,
Switzerland, 5-9 July, 2004, p. 153-155
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A review of fast beam chopping, F. Caspers,
Proc. of Linac 04, Lubeck, Germany, 16-20
August, 2004, p. 578-582.CARE-Conf-04-???-HIPPI
Slow-wave electrode structures for the ESS 2.5
MeV fast chopper,M.A. Clarke-Gayther, Proc. of
PAC 2003, Portland, Oregon, USA, 12-16 May, 2003,
p. 1473-1475 A Fast Chopper for the ESS 2.5 MeV
Beam Transport Line, M. A. Clarke-Gayther Proc.
of the eighth EPAC, Paris, France, 3-7 June,
2002, p. 2136-2138 Slow-wave electrode
structures for the ESS 2.5 MeV fast chopper,
M.A Clarke-Gayther,Proc. of the Eighth EPAC,
Paris, France, 3-7 June, 2002, p.2133-2135 Modul
ator systems for the ESS 2.5 MeV Fast Chopper,
M.A Clarke-Gayther,Proc. of PAC 2001, Chicago,
18-22 June 2001, p. 4062-4065.
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Unipolar AC coupled FPG baseline droop