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) Thomas Hofmann CERN – Beam Instrumentation (BE/BI/PM)

Contents Overview & Simulations 3 MeV Test Setup Preliminary Results 2

CERN Accelerator overview 3 LINAC 4 LHC luminosity upgrade!

LINAC 4 overview 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

Diamond Detector 5 H - beamH 0 beamlet < 1 ppm beamlet after drift Principle: H-H- H0H0 Bending Magnet x-scan y-scan H - beam Concept of Laser Emittance Meter for 160 MeV Pulsed Laser 1064 nm NON invasive!

Laser-Particle Interaction 6 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 M 2 < 3 for diameter < 200 µm P Peak > 1 kW Ref: J.T. Broad and W.P. Reinhardt, Phys. Rev. A14 (6) (1976) 2159

Stripping & propagation to detector 7 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/e 2 ): = 150 µm Rayleigh length = 10 mm

Contents Overview & Simulations 3 MeV Test Setup Preliminary Results 8

3 MeV Testbench MeV 100 MeV 50 MeV Transfer line to PSB Testbench

10 Setup at 3 MeV Diagnostics Testbench Focusing system

Lasers 11 Laser MOPA Fiberlaser (used at 3MeV) Solid-State (as reference) Energy per pulse0.1 mJ50 mJ Diameter~ 150 µm P 3 MeV0.5 %100 % t pulse 110 ns5 ns Repetition rate60kHz10 Hz Beam transportFiberFree Space

Integration Laser Setup 12 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

Optical setup 13 Focusing & Diagnostics 5m LMA fiber (20/130 µm; NA =0.08) Photodiode CCD with filterwheel on stage Focusing lensBeam Expander Fiber input with collimator lens Laser – Fiber Coupling H - Beam

Detector 14 Diamond Detector TypePolycrystalline Diamond on ceramics PCB Size20 x 20 mm Resolution5 channels Thickness500 µm Readout46 dB; 300 MHz preamplifier CIVIDEC Instrumentation, Austria Scope 50 Ohm 500 V Preamp 1 µF

Ref: G. Mann et al: ›Nanosecond laser damage resistance of differently prepared semi-finished parts of optical multimode fibers‹, Applied Surface Science 254, pp (2007) Troubleshooting Burned fiber end-facets – ~ 250 J/cm 2 Noise of motor driver on signal of diamond detector Pre-amplifiers for Diamond 15

Contents Overview & Simulations 3 MeV Test Setup Preliminary Results 16

Preliminary Results Raw signal Beam profile Vertical emittance 17

Outlook 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)

Thanks for your attention! 19