front end test stand — wp2 lead author: david findlay accelerator division isis department...
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Front end test stand — WP2
Lead author:David FindlayAccelerator DivisionISIS DepartmentRutherford Appleton Laboratory
Michael Clarke-GaytherAlan LetchfordJohn Thomason
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Why interest in front end?
Front end of machine is where
currents and duty cycles are set for whole machine
beam quality is set for whole machine
UKNF: 5 MW — Front end must be good!
Multi-megawatt proton accelerators are new
Neutrino factories
Neutron sources, transmutation,tritium, energy, etc.
1 W/m loss max., ~10—7 loss per metre
Strong overlap
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Neutrino factory proton driver:
Ion source (65 mA)
LEBT (low energy beam transport)
RFQ (75 keV 2.5 MeV, 280 MHz)
Chopper (typically ~30% chopped out)
DTL (2.5 MeV 180 MeV, 280 MHz)
Achromat
Synchrotrons
Need a front end test stand!
Front end
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Ion source: H—, 65 mA, 400 µs
2 × 2 × world’s leading H— source — ISIS
Existing negative ion source development programme at RAL for HPPAs in general
ASTeC
EU (network HPRI-CT-2001-50021)
This programme a benefit to front end test stand programme
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Ion Source Development Rig at RAL
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LEBT and RFQ
Low energy beam transport
Matches 65 mA from ion source to RFQ
RFQ
4-rod, 75 keV 2.5 MeV, 280 MHz
These less of a problem
Can base on experience of LEBT and RFQ for ISIS
More a matter of implementation than R&D
But ~1–1½ MW RF driver required for RFQ
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Beam loss
Why chopper?
Ion source Linac Ring
Bunching
Also to minimise RF transients and control beam intensity
>10 × ISIS
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No beam loss
Ion source Linac Ring
Bunching
With chopper — gaps in beam
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Good
Bad
Chopper performance required
DC accelerator
RF accelerator
ns – µs spacing
UKNF: 280 MHz, bunch spacing 3.57 ns
On
Off
Switch between bunches
Partially chopped bunches a problem! Tune shifts!
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Choppers across the world:
SNS 402 MHz, slow — only chopper built
CERN 352 MHz, power dissipation?
RAL 280 MHz, fast, rugged, “UK”
SNS, 2½ ns per bunch
LEBT MEBT
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RAL aspiration: switch in 2 ns and dissipate ~3–4 kW (when “off”)
2-stage process
Slow transmission line
Lumped line — thermally hardened
1
0
1
02 ns 8
ns
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RAL beam chopper— outline scheme
Need to build andtest with bunched beam
Beam
~1 m
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Ion source (R&D already
under way)
LEBT
RFQ (bunches beam)
Chopper
Diagnostics
Experience of building test stands at RAL — ISIS RFQ test stand
Build test stand
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Front end test stand at RAL — costsSY £k (hardware incl.
VAT +
contingency)
Overall design + infrastructure 8 398
Ion source 7 347
LEBT 5 231
RFQ 14 1388
Chopper 48 1990
4355 hardware
185 travel
82 4495 staff
9035 total
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Front end test stand at RAL — time scales
Outline design Expect to build in R8 at RAL
Specifications Including monitoring/control specifications
Install infrastructure Electricity, air, water, (lead) shielding, initial monitoring/controls
Procure & install mechanical support structures HV platforms, LEBT + RFQ + chopper supports, etc.
Develop, procure & install ion source Source, vac., HV sys., arc & extract drivers, monitoring/control
Design, procure & install LEBT (incl. diagnostics) 3-solenoid LEBT incl. emittance scanners
Design, procure & install RF driver for RFQ 1½ MW likely to be required
Design, procure & install RFQ 2–3 MeV, 4-rod, based on existing ESS design
Chopper: design & test off-line Slow & fast deflection systems without beam
Chopper: design complete system Incl. quadrupoles & RF buncher cavities
Design, procure & install beam diagnostics (at output of chopper) Long. & trans. emittances
Chopper: procure & install
Run complete test facility
2009–10 2010–11 2011–122005–06 2006–07 2007–08 2008–092004–05
Year 5 Year 6 Year 7 Year 8Year 1 Year 2 Year 3 Year 4
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Front end test stand at RAL
Six-year programme to build
Costed on basis of test stand already built and working
~£4½M equipment
~80 staff-years
RAL + university staff
Physics and engineering of real accelerator facility