Discussion on beam meaurements and objectives

1. What is the minimum that needs to be measured to validate an RFQ.2. What else would be of benefit to measure.3. What was in the previous 3MeV Diagnostics line.

Questions:

What was in the previous 3MeV Diagnostics line

TEST BENCH

Top view in bldg. 152

BCT

BPM

- 2 BCTs- 3 BPMs- Slit + SEMgrid- Halo monitor- BSM/Feshenko- CEA dipole 28.5 deg- 2 dumps

Back in 2013…Diagnostics test bench used for 3 and 12 MeV commissioning

EDMS 1004908EDMS 1134059

- 13/03/2013: first beam current measurements through inline and bent arm to validate RFQ transmission and beam average energy (dipole set for 3 MeV beam energy): 75% max transmission at 390kW nominal applied RF power for a ~12mA beam

- Transmission scan as function of RF power and LEBT vacuum pressure (H2 gas flow)

2013 RFQ commissioning

CERN-ACC-2013-0259

Transverse measurements via beam scraping with slit edge (emittance meter not operational yet)

Twiss parameters and emittance were reconstructed via 3 gradients’ method on profile measurements taken at different quad settings

0

2

4

6

8

10

0 2 4 6

RM

S b

eam

siz

e (

mm

)

Quad settings (A.U.)

Hor. RMS sizes

Measurement

From RFQ simulated

With Reconstructed

Longitudinally, it was measured that 95% of the beam was at the correct beam energy (BCT). No energy spread measurements were taken (in principle indirectly via knowledge of dispersion in the spectro line)

2013 RFQ commissioning

Last week of measurements in proton mode to check higher beam intensity performance.

Nota bene:

1) The 2013 test bench design was designed to be operational at 3 and 12 MeV

2) The test bench was built for installation in bldg. 152 and in the Linac4 tunnel it had to satisfy integration constraints, notably the max bending angle of the spectrometer magnet,

limited to 28.5 deg

3) The spectrometer magnet itself was since returned to CEA.

No point to replicate the same test bench design …

What is the minimum that needs to be measured to validate an RFQ.

Measurements

Transmission at nominal powerTransmission vs RFQ RF power (scan)Average beam energyBeam energy spreadTransverse beam profiles/emittance

Test bench needs

Straight + bent arm2x entrance quadrupoles to match the beam 3x BCTsSector bending magnet2x Slits (horizontal and vertical)3+1 x Harps/profile monitors steerers2x dumps

What else would be of benefit to measure

Measurements

Longitudinal phase space

Test bench needs

BSM in bent line1+ slit

Additional desiderata

- Proton operation : Compatibility of the test bench with proton operation is important to study possible differences in RFQ performance with protons and H-.

- Modularity/upgradeability:The diagnostics test bench should be built leaving open the possibility of future upgrades/device interchanges for potential re-use to test different structures/facilities (for example building individual supports for the devices etc)

- CEA bending magnet was returned to its owner. Need to find an alternative option (new or recycled), preferably a sector-type magnet, with higher bending angle to have a measurement resolution of a few percent (at least 40 deg, 90deg would be ideal). Additional compatibility at 45keV would allow for operation on the source test stand (energy spread measurements at source extraction/RFQ input).

- WP8 to find out if any parts of the old test bench are still available to be recycled.

- BI should be contacted and involved in discussions for proposing suitable diagnostics solutions.

- Beam dynamics studies are needed to finalize/validate the test bench design. ~8 months of technical student/fellow needed. End of year timeline?

General considerations

Extra slides

Alternative test bench layouts: BTF at SNS

A Aleksandrov, IPAC2017

Output current vs RF field amplitude

RFQ output beam energy via TOF

Transverse emittance via slit-slit-collector measurements

Longitudinal emittance from BSM profiles

JPARC setup