Proposal of a compact repetitive dichromatic x-ray generator with millisecond duty cycle for medical applications

Abstract

Many practical applications of X-rays lie in the important for the society fields of medical imaging, custom, transport inspection and security. Scientific applications besides of fundamental research include material sciences, biomicroscopy, and protein crystallography. Two types of X-ray sources dominate now: conventional tubes and electron accelerators equipped with insertion devices. The first are relatively cheap, robust, and compact but have low brightness and poorly controlled photon spectrum. The second generate low divergent beams with orders of magnitude higher brightness and well-controlled and tunable spectrum, but are very expensive and large in scale. So accelerator based Xray sources are mainly still used for scientific applications and X-ray tubes -in commercial equipment. The latter motivated by the importance for the society made an impressive progress during last decades mostly due to the fast developments of radiation detectors, computers and software used for image acquisition and processing. At the same time many important problems cannot be solved without radical improvement of the parameters of the X-ray beam that in commercial devices is still provided by conventional X-ray tubes.Therefore there is a quest now for a compact and relatively cheap source to generate X-ray beam with parameters and controllability approaching synchrotron radiation. Rapid developments of lasers and particle accelerators resulted in implementation of laser plasma X-ray sources and free electron lasers for various experiments requiring high intensity, shrt duration and monochromatic X-ray radiation. Further progress towards practical application is expected from the combination of laser and particle accelerator in a single unit for efficient X-ray generation. BASICS AND APPROACHIn this project a compact repetitive dichromatic X-ray source (see Fig. 1a) based on novel laser and electron accelerator systems is proposed for medical applications. X-rays originate from Thomson scattering of counter propagating laser and electron beams. Such a "laser-accelerator" approach is very flexible in providing an X-ray beam with properties required by numerous medical applications.As a typical example, requiring a high power X-ray beam, coronary angiography is considered here, which is the leading method of imaging of coronary arteries. More than one million coronary angiography diagnostic procedures per year are applied in the US to evaluate the patient's conditions and choose the best heart treatment strategy. The method is not completely safe, however. Prior to X-ray exposure a portion of iodine contrast agent is injected with a catheter (inserted through a groin or an arm) directly into the coronary artery of interest. Therefore there is a risk of blood vessel damage and high radiation dose exposure for patient and doctor. To avoid the risk and make coronary artery imaging a routine screening procedure, several alternative noninvasive approaches have being developed [1], [2]. The most promising one uses the dichromatic sync...

Enhanced optical cooling system test in an electron storage ring

“…Note that the damping time for the longitudinal direction does not depend on x;kick and one for the transverse direction is inverse to x;kick . Factor 6 in (10) takes into account that the energy spread for cooling is 2 E;0 , electrons meet less often with their URWs (screening effect), and that the jumps of the electron energy and closed orbit in general case lead to lesser jumps of the amplitude of synchrotron and betatron oscillations [6]. It does not take into account the decrease in efficiency of the interaction of the electron with its URW if the angular and the energy spreads of the beam are higher the limiting values [see (4) and (14)].…”

“…x , corresponding spreads in the positions of the closed orbits and in betatron amplitudes at N cl ph < 1 and at the number of photons produced by N s ÿ 1 extraneous electrons and noise photons in the sample N cl ph; ' N cl ph N s ÿ 1 N n > 1 are E max loss P max loss =fN cl ph of the electron in the fields of the kicker undulator and its amplified URW, N e;s is the number of electrons in the URW sample, N n is the number of noise photons in the URW sample at the amplifier front end [6,7]. Note that the energy jump E max loss corresponds to emission by signal electron in the pickup undulator of one-photon in the URW.…”

“…In some cases a controllable variable in the time optical delay line can be used to change in situ the length of the light pass-way between the undulators during the cooling cycle to keep the decelerating phases of electrons in the kicker undulator in the process of cooling [6,7].…”

“…Using the number of kicker undulators N kick > 1 permits one to cool the beam either in two directions or in one (transverse or longitudinal) direction by selecting distances between kicker undulators and time delays of the optical line [4,6].…”