[email protected] Laser based Emittance Measurement for LINAC4 Project Overview & Current Status T. Hofmann, E. Bravin, U. Raich, F. Roncarolo, F.

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Laser based Emittance Measurement for LINAC4

Project Overview & Current Status

T. Hofmann, E. Bravin, U. Raich, F. Roncarolo, F. Zocca (CERN)G. Boorman, A. Bosco, S. Gibson, K. Kruchinin (RHUL)

08.5.2014

Thomas HofmannCERN – Beam Instrumentation (BE/BI/PM)[email protected]

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Contents

• Overview & Simulations• 3 MeV Test Setup• Preliminary Results

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CERN Accelerator overview

LINAC 4

LHC luminosity upgrade!

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LINAC 4 overview

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160 MeV

100 MeV

50 MeV

Transfer line to PSB

Linac length ~ 80 m

Laser Emittance Meter

• Particles: H- ions• Top Energy: 160 MeV• Current: 40 mA• Pulse length: 400 µs

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DiamondDetector

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H- beam H0 beamlet< 1 ppm

beamletafter drift

Principle:

H-

H0

Bending Magnet

x-scan

y-scan

H- beam

Concept of Laser Emittance Meter for 160 MeV

Pulsed Laser1064 nm

NON invasive!

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Laser-Particle Interaction

• Stripping Probability

• In rest frame of H- beam:– Lorentz-Shift of Photon Energy– – At 160 MeV: 1064 nm -> 909 nm

Laser requirements:• Laser wavelength: 1064 nm • M2 < 3 for diameter < 200 µm• PPeak > 1 kW

Ref: J.T. Broad and W.P. Reinhardt, Phys. Rev. A14 (6) (1976) 2159

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Stripping & propagation to detector

Laser

Drift

3.0 m

• Emittance measurement possible via vertical detector scan

• H- Beam• Size (1 Sigma): y = 1.6 mm• Div (1 Sigma): y’ = 2.2 mrad

• Laser Beam• Size (1/e2): = 150 µm• Rayleigh length = 10 mm

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Contents

• Overview & Simulations• 3 MeV Test Setup• Preliminary Results

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3 MeV Testbench

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160 MeV

100 MeV

50 MeV

Transfer line to PSB

Testbench

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Setup at 3 MeV Diagnostics Testbench

Focusing system

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Lasers

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Laser MOPA Fiberlaser (used at 3MeV)

Solid-State(as reference)

Energy per pulse 0.1 mJ 50 mJ

Diameter ~ 150 µm ~ 150 µm

Pstrip @ 3 MeV 0.5 % 100 %

tpulse 110 ns 5 ns

Repetition rate 60kHz 10 Hz

Beam transport Fiber Free Space

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Integration Laser Setup

Diagnostics rack

Linear stage with 500 mm lens

Class 4 fiber laser

Coupling

tube

PXI-System

Ref: Fiber Laser Transport for the Photodetachment Emittance Measurements at FETS, Alessio Bosco

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Optical setup

Focusing & Diagnostics

5m LMA fiber (20/130 µm; NA =0.08)

Photodiode

CCD with filterwheel on stage

Focusing lens Beam ExpanderFiber input with collimator lens

Laser – Fiber Coupling

H- Beam

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Detector

Diamond Detector

Type Polycrystalline Diamond on ceramics PCB

Size 20 x 20 mm

Resolution 5 channels

Thickness 500 µm

Readout 46 dB; 300 MHz preamplifier

CIVIDEC Instrumentation, Austria

Scope

50 Ohm

500 V

Preamp1 µF

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Ref: G. Mann et al: ›Nanosecond laser damage resistance of differently prepared semi-finished parts of optical multimode fibers‹, Applied Surface Science 254, pp.1096-1100 (2007)

Troubleshooting

• Burned fiber end-facets– ~ 250 J/cm2

• Noise of motor driver on signal of diamond detector

• Pre-amplifiers for Diamond

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Contents

• Overview & Simulations• 3 MeV Test Setup• Preliminary Results

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Preliminary Results

• Raw signal

• Beam profile

• Vertical emittance

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Outlook

• 12 MeV Testbench– 10 m LMA fiber for laser transport– Particles traverse diamond detector

• 160 MeV setup– Detector (Readout & Calibration)– Fiber delivery setup (20 m needed)

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Thanks for your attention!

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