Progress on the RAL Linac Design

- HIPPI Yearly Meeting –- CERN, Geneva -

29.10.2008

- C. Plostinar -

Presentation outline

• Upgrades for ISIS

• FETS Overview

– End to end beam dynamics simulations in FETS

• The new RAL linac

• Conclusions

400 MeV LinacCollimating Achromat

(Linac upgrade to 800 MeV)

An upgrade option for ISIS

TS-3

3 GeV 50 Hz Ring

Proposed upgrade (staged approach):

- Isis Now: 800 MeV, Beam Power: 0.16–0.24 MW

- Adding a ~3 GeV RCS -> ~1MW

- Adding a 400 MeV linac will increase the beam power up to 2 MW

- Increasing the linac energy to 800 MeV provides upgrade options to 5 MW

TS-1

TS-2

Linac Layout

Front End

DTL (Drift Tube Linac) SCL (Side Coupled Linac)

324 MHz 972 MHz

3 MeV

180 MeV

90 MeV

180 MeV Linac Layout (old)

800 MeV Linac Layout (new)

Front End DTL CCL ScL 1 ScL 2

3 MeV 75 MeV 193 MeV 409 MeV 800 MeV

324 MHz 648 MHz

H- Ion source

LEBT MEBT RFQ

The Front End Test Stand (FETS)

Front End Overview

Magnetic LEBT

RFQ

MEBT and chopper

H− ion source

Laser profile monitor

Front End Overview

- The beamline support stands and rail system are installed in preparation for ion source and LEBT installation.- View of the HV cage showing the platform and installed equipment - Ion Source vessel in situ

FETS End to End Beam Dynamics Simulations

LEBT MEBT RFQIon

Source

The measured emittance (already improved by a factor of two in the last year) is more than a factor of two larger than the waterbag particle distribution used for the optimization of the individual elements.

Waterbag (Ex=Ey=0.25 Pi.mm.mrad (RMS))

Measured (Ex=0.58, Ey=0.52)

FETS End to End Beam Dynamics Simulations

LEBT MEBT RFQIon

Source

The slight s-shaped aberrations show the influence of non linear magnetic fields on the beam transport but the emittance growth is reasonable.

WaterbagEx=Ey=0.33

MeasuredEx=0.69, Ey=0.64

FETS End to End Beam Dynamics Simulations

LEBT MEBT RFQIon

Source

The large input emittance for the real beam causes large (transversal) particle loss in the RFQ which causes an overall reduction of the emittance.

WaterbagEx=0.28, Ey=0.27

MeasuredEx=0.46, Ey=0.47

FETS End to End Beam Dynamics Simulations

LEBT MEBT RFQIon

Source

Particle losses in the MEBT can be neglected for the ideal case and is < 10% for the real beam distribution.

WaterbagEx=0.30, Ey=0.34

MeasuredEx=0.40, Ey=0.49

FETS End to End Beam Dynamics Simulations

P1 P2 P3 P488%

90%

92%

94%

96%

98%

100%

FETS Transmission (Waterbag Dist.)

Tran

smis

sion

P1 P2 P3 P430%40%50%60%70%80%90%

100%

FETS Transmission (Measured Dist.)

Tran

smis

sion

- Transmission more than 90% for the waterbag distribution (100% - LEBT, 95% - RFQ, 98% - MEBT)

- Much higher losses when using the measured distribution – 46% transmission (100% - LEBT, 52% - RFQ, 89% - MEBT)

FETS End to End Beam Dynamics Simulations

P1 P2 P3 P400.050.1

0.150.2

0.250.3

0.350.4

FETS Emittance Evolution (Waterbag Dist.)

Emit

tanc

e

P1 P2 P3 P400.10.20.30.40.50.60.70.8

FETS Emittance Evolution (Measured Dist.)

Emit

tanc

e- Moderate emittance growth when using the ideal distribution- Emittance reduction when using the real distribution due to high beam

loss- Efforts to reduce the ion source emittance and increase the RFQ

acceptance are under way.

The H- Linac Design

MEBT DTL CCL ScL 1 ScL 2

3 MeV

75 MeV

193 MeV

409 MeV

800 MeV

324 MHz 648 MHz

RFQLEBTIon Source

Key Linac Parameters:- Ion Species: H-- Energy: 3 – 800 MeV- Beam pulse current before MEBT chopping: 43mA- Beam pulse current after MEBT chopping: 30 mA- Beam power 0.5 MW- Repetition Rate: 50 Hz- Sections:

- RFQ- Drift Tube Linac (4 tanks)- Coupled-Cavity Linac (56, 10 cell cavities)- Superconducting Linac (69, 5/6 cell cavities)

~11 m ~280 m

The DTL Section• Input energy: 3 MeV• Output energy: 75 MeV• Operating frequency: 324 MHz

Energy (MeV)

No of cells

Sync. Phase (deg)

Power

Tank 1 3 – 19.6 62 -42 -> -35 1.695

Tank 2 19.6 – 38 39 - 34.5 -> -32

1.699

Tank 3 38 – 56 35 -35 -> - 32.5

1.637

Tank 4 56 – 75 31 -33 -> -30 1.664

• Toshiba Klystrons (2.5 MW)• Compact PMQs (or hybrid

quadrupoles?)• No of tanks: 4 (1 Klystron /Tank)• E field 2.5 MV/m• Maximum E field level: 1.5 Kilpatrick

The H- Linac Design

DTL Simulations for the RAL linac

Beam envelopes in DTL, CCL, ScL1 & ScL2

Phase space plots at CCL output

Phase space plots at ScL2 output

Normalised emittance evolution (RMS)

MEBT MEBT DTL1 DTL2 DTL3 DTL4 CCL ScL1 ScL2Input Output Output Output Output Output Output Output Output

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Emittance Evolution along the Linac

Nor

mal

ized

RM

S Em

itta

nce

Klystron requirements

Stage Number Freq (MHz) Peak Power

RFQ and DTLs 5 324 2.5CCL (56 cavities)

5 648 5.0

ScL1 (36 cavities)

9 648 1.6

ScL2 (34 cavities)

9/17 648 5.0/1.6

Also needed: amplifiers for four 324 MHz MEBT bunchers, and one 648 MHz buncher between DTL4 and CCL

Studies now required:

1. MEBT optics re-evaluation.

2. Alternatives to DTL & CCL + Shunt Impedance Studies.

3. CCL & ScL 648 & 972 MHz comparisons.

4. Refine designs of various linac stages (matching, etc.).

5. Error effect evaluation for the full linac.

6. Effect of failed superconducting cavities.

7. Design of phase ramping, ring beam line.

Conclusions

• A new ISIS upgrade plan has been identified and it includes a possible 800 MeV linac

• Work on the new linac has started

• Work on the FETS project is progressing well