1. Laser system for ILC diagnostics Sudhir Dixit: The John Adams Institute (Oxford)

2. Two main features of ILC 1.High accelerating gradient – High energy (TeV) & high average power (10s MW) lepton beams 2. Low emittance, very small size lepton beams - High Luminosity (10 34 cm -2 s -1 ) We, at oxford, plans to develop a suitable laser to map the time resolved e - /e + beam emittance/luminosity within a single ILC pulse of 950 s Method To measure the e - /e + bunch profiles/sizes within a single ILC pulse with a sub-micron resolution, high-coherence, high average power mode-locked laser all along the 40 km accelerator complex Damping ring Linac Beam delivery section

3. ILC e-/e+ pulse structure ILC beam sizes

4. Methodology of Lepton beam size estimation: Laser-wire Vertical scanning:  y Horizontal scanning:  x

5. We plan to have about 100 measurements within an ILC pulse by time synchronised laser and e-/e+ pulses and fast, EO/Piezo, laser deflectors The LASER-WIRE

6. Guidelines on the choice of Laser for the LASER-WIRE f laser = f emicrobunch (3 MHz, timing accuracy < 0.5 ps, Mode locked laser) 2. Laser pulse duration, t micro and t macro T micro = e - bunch length (0.5 mm) = 2 ps (But may be relaxed to 10 ps) T macro = 950 s (Long pulse ML Laser) 3. Laser spot size,  L  m 2 =  e 2 +  L 2 +  L jitter 2 +  e jitter 2 + …… We require,  jitter <  L <  e [ L  1 m] Gaussian profiles in space and time, TEMoo mode spatial coherence (M 2  1) Focussing lens f # = 1.5-2 4. No. of Comptons (N C ) & Laser peak power (P) N C =P N e  C h -1 c -2  -1/2  m -1/2 exp [- 0.5 (/ m ) 2 ] For good accuracy, N C > 2000 and good energy stability. This requires P  10MW (100 J/10ps) 1. Laser repetition rate, f laser 5. Laser wavelength, L & Rayleigh Range, R L We want, R L = 4  L 2 / =  x and  L <  Y Also we know,  C reduces as L is reduced  L  M 2 f # The net choice L = 250 nm – 500 nm

7. The The Laser system The laser system has to be an master oscillator followed by power amplifier/s (MOPA) Laser oscillator choice: A conventional mode-locked Nd:YLF (1047 nm/1053nm) or Nd: YAG (1064 nm) laser A mode-locked fiber laser (1047/1053/1064 nm) Laser Amplifier choice: High power diode pumped Nd:YLF or Nd:YAG Choice on 2 nd harmonic crystal : LBO/BBO (250 nm – 500 nm)

8. Attractiveness of Fiber laser baser oscillator-preamplifier systems High quality beams: Diffraction limited divergence, excellent beam profiles, very low pointing jitter, pulse-width – from 100 fs to 10 ps, rep. Rate = KHz to 10s of MHz Available pulse energies: 10 micro-joules (6 MHz, 1 ps pulses) 1000 micro-joules (50 KHz, 200 fs pulses) Issues to be resolved: Exact rep. Rate control and synchronization to external signal

9. Current status: Vendors are being contacted for part of laser systems/components The proof of principle will be tested in ATF-2 at KEK on pulse structure similar to ILC The laser being developed for ‘The laser-wire’ will have some overlapping with the laser systems used in Photo-injector Polarimeter In long term future, one may think about suitable laser for   collider experiments! Thank You