Front end test stand — WP2 Lead author: David Findlay Accelerator Division ISIS Department...
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Transcript of Front end test stand — WP2 Lead author: David Findlay Accelerator Division ISIS Department...
Front end test stand — WP2
Lead author:David FindlayAccelerator DivisionISIS DepartmentRutherford Appleton Laboratory
Michael Clarke-GaytherAlan LetchfordJohn Thomason
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
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
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
Ion Source Development Rig at RAL
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
Beam loss
Why chopper?
Ion source Linac Ring
Bunching
Also to minimise RF transients and control beam intensity
>10 × ISIS
No beam loss
Ion source Linac Ring
Bunching
With chopper — gaps in beam
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!
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
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
RAL beam chopper— outline scheme
Need to build andtest with bunched beam
Beam
~1 m
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
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
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
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