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COBALD - An Inverse Compton Back-Scattering (CBS) Source at Daresbury.

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Presentation on theme: "COBALD - An Inverse Compton Back-Scattering (CBS) Source at Daresbury."— Presentation transcript:

1 COBALD - An Inverse Compton Back-Scattering (CBS) Source at Daresbury

2 Introduction to ALICE ALICE (Accelerators and Lasers In Combined Experiments) - known formerly as ERLP: High-voltage DC photoemission electron gun; Superconducting linacs operating in energy recovery mode; A mid-IR free-electron laser (FEL); PLUS a source of ultrashort x-ray pulses produced by inverse Compton scattering of multi-terawatt 100 fs laser pulses by the electron beam.

3 ALICE Layout

4 Nominal ALICE Parameters Gun Energy350keV Injector Energy8.35 MeV Circulating Beam Energy35 MeV Linac RF Frequency1.3 GHz Bunch Repetition Rate81.25 MHz Nominal Bunch Charge80 pC Average Current13 µ A

5 Status Gun currently fitted with “Stanford ceramic” – limits operating voltage to ~250 kV; Gun diagnostic test line gone - ready for beaming into booster module and beyond; Booster module warm window cracked & replaced – investigation underway; Shutdown on 25 th October; 3 weeks operation in Dec - ~ 6 months operation in 2009; Priorities – energy recovery, injector tuning, diagnostics, CBS…

6 Compton Back-Scattering Compton scattering of photons off a high-brightness electron beam: A collision between a photon and an electron; Or the electromagnetic field of the laser beam acts as a very short period undulator; Produces ultra-short pulse x-ray radiation from low-energy e - beam; Collision geometry determines flux and energy.

7 COBALD COmpton BAckscattering x-ray source driven by the multi-10 TW Laser installed at Daresbury


9 Optics for both possible interaction angles: 180  “head-on” and 90  “sideways-on”

10 ALICE and CBS parameters ParameterValueUnits Energy at interaction point 35MeV Train repetition rate10Hz Bunches per train1 Bunch charge80pC Electrons per bunch5×10 8 Average current0.8nA Peak current6.5mA ParameterValueUnits Brightness>10 20 photons/mm 2 /mrad 2 / s/0.1% bandwidth Peak x-ray energy 30keV (head-on geometry) 15keV (sideways-on) X-ray pulse length (rms) 350fs (head-on geometry) 100fs (sideways-on) X-ray source size (FWHM) 20 × 35 μmμm

11 X-ray output The angular distribution of the x- rays for head-on collision geometry collision; each colour is a 1 keV energy band with 20-21 keV on outside and 30-31 keV at centre

12 FEL wiggler to remain in place (  no extra quadrupoles); Smallest possible transverse electron beam size at interaction point; After photon-electron interaction most of e - beam must make it round the second arc Lattice 8.4 used as starting point Figure shows lattice 8.5; only slightly different!

13 Giving: Beam waist 13.45 × 19.81 μ m (  x ×  y ); 99% of the electrons making it to the pop-in dump. Lattice re-optimised using ELEGANT

14 Beamsize OK?

15 Quadrupole gradients must be within existing power supply range; No apparent problem for beam as far as pop up dump. Magnet power supplies OK?

16 NameLength 8.58.4_CBS 8.5 to 8.4_CBS 8.4_CBS Gradient CurrentGradient CurrentMax Currentc.f. max (m -2) (T/m)(A)(m -2 )(T/m)(A) Changecurrent INJ-MAG-QUAD-010.15-8.62-0.24-0.65-9.29-0.26-0.705.58%13% INJ-MAG-QUAD-020.159.500.260.7212.000.330.915.526%17% INJ-MAG-QUAD-030.152.630.070.20-9.09-0.25-0.695.5-446%13% INJ-MAG-QUAD-040.15-11.77-0.33-0.89-8.59-0.24-0.655.5-27%12% INJ-MAG-QUAD-050.1525.600.712.2725.600.712.273.90%59% INJ-MAG-QUAD-060.1510.910.300.979.550.270.853.9-12%22% INJ-MAG-QUAD-070.15-17.03-0.47-1.51-17.23-0.48-1.533.91%40% INJ-MAG-QUAD-080.1514.630.411.3014.720.411.313.91%34% INJ-MAG-QUAD-090.150.00 3.90% INJ-MAG-QUAD-100.1511.950.331.0611.950.331.063.90%28% INJ-MAG-QUAD-110.15-8.95-0.25-0.79-8.94-0.25-0.793.90%21% INJ-MAG-QUAD-120.1511.950.331.0611.950.331.063.90%28% ST1-MAG-QUAD-010.15241.200.140.302.240.260.586.894%9% ST1-MAG-QUAD-020.1524-3.35-0.39-0.94-4.61-0.54-1.286.837%19% ST1-MAG-QUAD-030.15247.300.851.967.290.851.966.80%29% ST1-MAG-QUAD-040.1524-5.91-0.69-1.63-4.66-0.54-1.296.8-21%19% AR1-MAG-QUAD-010.1511.431.333.6311.431.333.635.50%66% AR1-MAG-QUAD-020.15-5.35-0.63-1.70-5.36-0.63-1.705.50%31% AR1-MAG-QUAD-030.15-5.35-0.63-1.70-5.36-0.63-1.705.50%31%

17 NameLength 8.58.4_CBS 8.5 to 8.4_CBS 8.4_CBS Gradient CurrentGradient CurrentMax Currentc.f. max (m -2) (T/m)(A)(m -2 )(T/m)(A) Changecurrent AR1-MAG-QUAD-040.1511.431.333.6311.431.333.635.50%66% ST2-MAG-QUAD-010.1524-7.99-0.93-2.20-7.53-0.88-2.076.8-6%30% ST2-MAG-QUAD-020.15247.480.872.017.390.861.996.8-1%29% ST2-MAG-QUAD-030.1524-2.32-0.27-0.66-3.92-0.46-1.096.866%16% ST2-MAG-QUAD-040.15242.560.300.67-3.92-0.46-1.096.8-263%16% ST2-MAG-QUAD-050.15244.170.491.114.810.561.286.816%19% ST2-MAG-QUAD-060.1524-10.55-1.23-1.55-2.75-0.32-0.423.7-73%11% ST2-MAG-QUAD-070.152411.401.331.640.00 -0.023.7-101%0% ST3-MAG-QUAD-010.15240.00 -0.02-0.80-0.09-0.143.7626%4% ST3-MAG-QUAD-020.1524-4.69-0.55-0.7011.671.361.683.7-340%45% ST3-MAG-QUAD-030.152411.871.393.20-13.75-1.61-3.776.8-218%55% ST3-MAG-QUAD-040.1524-8.77-1.02-2.4114.921.744.046.8-267%59% AR2-MAG-QUAD-010.1510.821.263.434.490.521.435.5-58%26% AR2-MAG-QUAD-020.15-7.71-0.90-2.45-12.00-1.40-3.815.556%69% AR2-MAG-QUAD-030.15-7.71-0.90-2.45-5.36-0.63-1.705.5-30%31% AR2-MAG-QUAD-040.1510.821.263.434.490.521.435.5-58%26% ST4-MAG-QUAD-010.1524-7.56-0.88-2.08-9.72-1.13-2.676.828%39% ST4-MAG-QUAD-020.15248.060.942.1716.391.914.436.8104%65% ST4-MAG-QUAD-030.1524-1.66-0.19-0.530.00 5.5-100%0% Pop up dump

18 Summary ELEGANT used to re-optimise MAD-derived lattice 8.4 to give minimum beam size at interaction point, while: Wiggler stays in place; All of the beam makes it further round to the pop-up dump; Quadrupole gradients are compatible with existing PSUs; 10Hz, single bunch, so no energy recovery needed; First experiments next year.

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