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Front end test stand — WP2

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1 Front end test stand — WP2
Lead author: David Findlay Accelerator Division ISIS Department Rutherford Appleton Laboratory Michael Clarke-Gayther Alan Letchford John Thomason

2 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

3 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

4 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 ) This programme a benefit to front end test stand programme

5 Ion Source Development Rig at RAL

6 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

7 Also to minimise RF transients and control beam intensity
Why chopper? Ion source Linac Ring Beam loss >10 × ISIS Bunching Also to minimise RF transients and control beam intensity

8 With chopper — gaps in beam
Ion source Linac Ring No beam loss Bunching

9 Chopper performance required
DC accelerator RF accelerator ns – µs spacing UKNF: 280 MHz, bunch spacing 3.57 ns Switch between bunches Good On Off Bad Partially chopped bunches a problem! Tune shifts!

10 Choppers across the world:
SNS 402 MHz, slow — only chopper built CERN 352 MHz, power dissipation? RAL 280 MHz, fast, rugged, “UK” LEBT MEBT SNS, 2½ ns per bunch

11 Slow transmission line
RAL aspiration: switch in 2 ns and dissipate ~3–4 kW (when “off”) 2-stage process Slow transmission line 1 Lumped line — thermally hardened 2 ns 8 ns

12 RAL beam chopper — outline scheme
Need to build and test with bunched beam

13 Build test stand Ion source (R&D already under way) LEBT RFQ (bunches beam) Chopper Diagnostics Experience of building test stands at RAL — ISIS RFQ test stand

14 Front end test stand at RAL — costs
SY £k (hardware incl. VAT + contingency) Overall design + infrastructure Ion source LEBT RFQ Chopper 4355 hardware 185 travel staff 9035 total

15 Front end test stand at RAL — time scales

16 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

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