B. Azadegan, S. A. Mahdipour Hakim Sabzevari University Investigation of channeling radiation from diamond crystals to provide a mono energetic x ray at the ELBE electron linear accelerator B. Azadegan, S. A. Mahdipour Hakim Sabzevari University

Guideline Theory of channeling radiation (CR) Experimental setup CR measurements on diamond Intense chaneling radiation source

1. Theory of channeling radiation Planar channeling: One dimensional problem Axial channeling: two dimensional problem

1. Theory of channeling radiation - Lorentz factor - observation angle CR properties quasi-monochromatic directed intense tunable

1. Theory of channeling radiation Planar channeling The planar continuum potential of diamond for electrons Axial channeling The <100> axial continuum potential of germanium for electrons

1. Theory of channeling radiation Quantum mechanical model Channeling radiation Wave functions and eigenvalues CR intensity CR photon energy

1. Theory of channeling radiation 1→0 Yield (photons/e sr keV) 2→1 Photon energy (keV) Simulation of the CR spectrum for 42.5 μm thick diamond crystal Measurment of the CR spectrum for 42.5 μm thick diamond crystal Yield (photons/e sr keV) Photon energy (keV)

1. Theory of channeling radiation (b) Θ0=0.25 mrad (a) Θ0=0.0 Classical model Planar : Axial : Angular energy distribution:

2. Experimental setup ELBE = Superconducting Electron Linac of high Brilliance and low Emittance

2. Experimental setup The Superconducting Electron Linear Accelerator Parameter X-rays Bremsstrahlung IR, Neutrons, Positrons Electron beam energy / MeV 12 - 40 8 - 20 Max. bunch charge /pC 0.77 77 Max. average beam current /µA 200 1000 Normalized transverse emittance /mm mrad(rms) 3 20 Normalized longitudinal emittance /keV ps(rms) 50 140 Micropulse duration /ps 2 1 - 10 Micropulse repetition rate /MHz 260 13 Macropulse duration /ms 0.1 - 40 / cw Macropulse repetition rate /Hz 1 - 25  

Beam parameters for CR: 2. Experimental setup Radiation physics cave Quadrupole 1 Quadrupole doublet Dipole 1 Quadrupole 2 Goniometer chamber Beam dump Concrete wall Beam dump shielding Dipole 2 Vacuum pipe Shielding and collimator Detector with preamplifier e- beam Crystal To the amplifier and MCA Shutter Secondary electron monitor Faraday cup Parameters of CR from 1 – 0 transition in the (110) plane of diamond Photon energy ECR ≈ 10 ÷ 70 keV Flux density YCR ≈ 109 ÷ 1010 s-1cm-2 per 10% BW @ 1 m, 100 mA Beam parameters for CR: Energy Ee= 10 ÷ 35 MeV ∆Ee≈ 200 keV Current Ie  0.2 mA Emittance n rms ~ 3 p mm mrad

3. CR measurements on diamond Diamond structure: Diamond, Si,Ge Map of diamond crystal constructed from planar scans Planar CR out of (110), (111) and (100) planes Electron energies 14.6, 17, 25, 30 and 34 MeV Crystal thicknesses 42.5, 102, 168 and 500 μm

Processing of the spectra: 3. CR measurements on diamond Processing of the spectra: Correction for detector efficiency, selfabsorption and attenuation in window materials Subtraction of bremsstrahlung background Approximation of peak profiles for determination of CR parameters corrected measured Ee=17 MeV CdTe detector Counting rate Counting rate Photon energy (keV) Photon energy (keV) Spectra of (110) planar channeling radiation (blue) and bremsstrahlung (green)

3. CR measurements on diamond Crystal thickness (µm) Photon energy (keV) Line width (keV) Photon yield (ph/(sr e-)) Observed Calculated 14.6 MeV 42.5 16.58 17.06 1.51 0.87 0.048 0.112 168 16.99 1.80 1.25 0.090 0.223 500 16.47 2.20 1.48 0.149 0.384 17 MeV 21.72 22.23 2.00 0.95 0.059 0.148 22.37 2.47 1.39 0.13 0.295 21.38 2.77 1.90 0.30 0.509 30 MeV 56.19 56.87 5.88 2.29 0.229 0.448 56.22 57.00 6.12 3.32 0.52 0.890 55.06 56.61 11.98 5.77 1.012 1.535 Scaling laws of main CR parameters extracted for the 1→0 transition in the (110) plane of diamond Conclusions: Photon energy scales with γ 1.7 Photon yield scales with γ 2.12 Photon yield scales with

4. Intense channeling radiation source An intense channeling radiation X-ray source came into operation at ELBE Diamond (110) Ee=14.6 MeV dN/dEx (Photon keV-1) Diamond crystal Photon energy (keV) Cooled CR target CR measured at 0◦ at Ie = 11 nA CR measured at 90◦at Ie = 80 μA Bremsstrahlung CR on-line monitoring at photon rates of 1010 s-1 by means of a Compton spectrometer CR X-ray source

4. Intense channeling radiation source

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