Abstract
Free-electron lasers (FEL) and synchrotron sources of high brilliance x-rays have proven to be of tremendous value in basic and applied research. Inverse-Compton sources (ICS) can achieve brilliance matching the requirements of many applications pioneered at those FEL and synchrotron facilities---including phase contrast imaging, macromolecular x-ray crystallography, and x-ray microscopy---but with size, cost, and complexity compatible with a small laboratory. The free-electron laser inverse-Compton interaction compact x-ray source at the University of Hawaii at Manoa is a unique approach to an ICS which employs an FEL as the laser source. We have measured a total average flux of $3.0\ifmmode\times\else\texttimes\fi{}{10}^{5}\text{ }\text{ }\mathrm{photons}/\mathrm{second}$ with an average brilliance of $2.0\ifmmode\times\else\texttimes\fi{}{10}^{7}\text{ }\text{ }\mathrm{photons}/\mathrm{s}\text{ }{\mathrm{mm}}^{2}\text{ }{\mathrm{mrad}}^{2}$ 0.1% of bandwidth (BW) with a peak energy of 10.9 keV from the source. While these results are modest in comparison to the standards set by other IC sources, upgrades to the system have the potential to increase the total average flux to $9.2\ifmmode\times\else\texttimes\fi{}{10}^{11}\text{ }\text{ }\mathrm{photons}/\mathrm{second}$ with an average brilliance of $1.9\ifmmode\times\else\texttimes\fi{}{10}^{12}\text{ }\text{ }\mathrm{photons}/\mathrm{s}\text{ }{\mathrm{mm}}^{2}\text{ }{\mathrm{mrad}}^{2}$ 0.1% BW: comparing more favorably to other sources. We discuss the scientific program, the progress made in design and development, and the achievements of the source to date. We also outline future upgrades and integration needed to yield an enabling source for emerging high brilliance x-ray applications.
Highlights
The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory and other advanced x-ray Free-electron lasers (FEL) and synchrotron light sources have proven the value of high brilliance x-rays for basic and applied research [1], but these sources cannot be used on a daily basis by a particular user
The optical transport system from the FEL to the interaction point (IP) employs a long run 3-inch diameter evacuated pipe to deliver the laser to the IP optical bench with minimum atmospheric absorption of the IR light, followed by a shorter path in ambient air allowing the insertion of accessible IR optical components that serve the following purposes: (i) collimating the laser beam, (ii) inserting a precision optical trombone delay line to adjust the synchronism of the optical pulses and electron bunches, and (iii) a final steering mirror and focusing lens to deliver and align a TEM00 Gaussian mode of 30 μm radius to the IP
The x-ray transport beam line and detection system consists of the following components: an x-ray scattering chamber, a beryllium window, a lead collimator, a helium purged beam pipe, a yttrium aluminum perovskite activated by cerium (YAP:Ce) scintillator, and a Hamamatsu 6199 photomultiplier tube (PMT)
Summary
The Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory and other advanced x-ray FEL and synchrotron light sources have proven the value of high brilliance x-rays for basic and applied research [1], but these sources cannot be used on a daily basis by a particular user. Laboratories (e.g., universities, hospitals, or semiconductor manufacturing facilities) making the benefits of high brilliance x-rays—previously available only at the national laboratory scale facilities—available for daily use to a broader range of users [2] These sources have applications emerging in many sectors including nuclear materials detection [3], small-angle x-ray scattering [4], phase contrast imaging [5], macromolecular x-ray crystallography for drug discovery [6], and x-ray microscopy [7]. In these ICS systems, high intensity laser pulses collide with electron bunches to produce x-rays with flux proportional to the product of the laser peak power and the average current of the electron beam (ebeam). Most current ICS approaches are restricted to sub-GHz repetition rates [9,10,11], and electron guns capable of GHz rep rates (for example [12]) have yet to be employed in ICS systems
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