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