The lith Symposium on Accelerator Science and Technology, Harima Science Garden City, 1997

INTENSE COHERENT BREMSSTRAHLUNG LIGHT SOURCEUTILIZING COMPACT ELECTRON ACCELERATORS
E.J.Minehara and E. Tanaka
Free Electron Laser Laboratory,
Department of Reactor Engineering, Tokai Research Establishment, Japan Atomic Energy Research Institute
2-4 Shirakata-shirane, Tokai-mura, Naka-gun, lbaraki-ken, 319-11 JAPANA bright, CW(continuous-wave), tunable source of Xrays and gamma-rays is proposed here. As illustrated inFig.l, the X-rays and gamma-rays are obtained from

Spatially Coherent Bremsstrahlung
Bremsstrahlung of wavelength A00coherent bremsstrahlung (Ueberall Effect 1) or the crystalAtoms
Latticeenhanced, monochromatized, and polarized variant of0ordinary bremsstrahlung) of the highly-intense, highlybright, monochromatic, and CW electron beam being
accelerated using a small superconducting rf Iinac like the0driver for the JAERI FEL. In the JAERI superconducting
rf-linac driven FEL, hard X-rays of several tens keV andgamma-rays of a few MeV would be generated using a15MeV electron beam energy and a slightly- inclined thin Fig.l, An illustrated explanation of coherent
single crystal. Like a klystron tube with a so-called
bremsstrahlung, that is, a so-called Ueberall Effectl,3).
depressed geometry, two main superconducting accelerator
15r--------------------- ----------------.
amodules of the JAERI superconducting rf-linac could be
T : 15 MeV
adjusted, and out of phase each other to recover the rf[tOO] DIRECTION
12- - - UNCOLLIMATED
energy, and to stabilize the rf field in the acceleratorpCOLLIMATED, Oc : fcavities during beam acceleration.
9Such an X-ray and gamma-ray source would beI
I
constitute a low cost and high performance compactII
6
alternative to the more traditional plasma X-ray laser,I/
synchrotron rings, X-ray tubes and so on. The coherent///
bremsstrahlung has about 100 times stronger intensity///
than the medium-sized synchrotron light source in the,,/several tens keV energy range 2). In comparison withPXR(parametric X-ray radiation) as another highlyintense X-ray source recently being proposed in the8.ooo.oeo.16o.24o.32

15 breference2), the coherent bremsstrahlung has a forwardpeaked along the electron beam direction, and a similar
angular distributions of ~ 1/y ( y =total electron energy
in unit of electron rest mass). We can realize narrower
bandwidth X-ray radiation with the use of proper
aperturing or collimating without the necessity ofmonochrometers. In the Fig.2 3\ the theoretical
calculations are shown with photon collimation of 9c=112

T •15MeV
12"' [ 100] DIRECTION

963o and the uncollimated, and the experimentals theuncollimated.
References
1) Kinbara T.: 1968, Shouka-Boh, "Kisobutsurigakuvol.2".
2) Baryshevsky V.G. and Feranchuk I.D.:J.Physique
44(1983)913-922.
3) Saenz A.W. andUeberall H.: Phys.
Rev.B25,4418(1982). Saenz A.W. andUeberall H.: 1985,
Springer-Verlag, "Coherent Radiation Sources".

Fig.2, a) Coherent part of bremsstrahlung spectrum of
T=15MeV electrons incident along the<lOO> direction ofa Si crystal at room temperature* with photon
collimation(---), and with photon collimation of 9c:::;;J/2o(-), b) As(a)( uncollimated ), but with ttie electrons
incident in the (001) plane at an angle of 9c=2· with the<100> direction3).

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