Isolated terawatt attosecond hard X-ray pulse generated from single current spike

Isolated terawatt (TW) attosecond (as) hard X-ray pulse is greatly desired for four-dimensional investigations of natural phenomena with picometer spatial and attosecond temporal resolutions. Since the demand for such sources is continuously increasing, the possibility of generating such pulse by a single current spike without the use of optical or electron delay units in an undulator line is addressed. The conditions of a current spike (width and height) and a modulation laser pulse (wavelength and power) is also discussed. We demonstrate that an isolated TW-level as a hard X-ray can be produced by a properly chosen single current spike in an electron bunch with simulation results. By using realistic specifications of an electron bunch of the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL), we show that an isolated, >1.0 TW and similar to 36 as X-ray pulse at 12.4 keV can be generated in an optimized-tapered undulator line. This result opens a new vista for current XFEL operation: the attosecond XFEL

A bunch compressor for the CLIC main beam

The last bunch compressor chicane in front of the main linac of the multi TeV linear collider CLIC is foreseen to longitudinally compress the incoming electron bunches from $σ_s$ = 250 μm to $σ_s$ = 30 μm. It is specified that the emittance growth in this chicane, which is mainly due to incoherent and coherent synchrotron radiation, should not exceed 30 nm rad in the horizontal plane and 1 nm rad in the vertical plane. To achieve these values the chicane layout and the optics functions have been optimized and the influence of shielding due to the vacuum chamber has been studied. The importance of the CSR micro bunch instability is discussed. Chicane layouts and the corresponding electron beam parameters are presented, which allow to preserve the emittance within the specifications

Designing a bunch compressor chicane for a multi-TeV linear collider

Incoherent and coherent synchrotron radiation are issues in most new accelerator projects utilizing bunch compressors to increase the peak current of the electron beam. Here we present a systematic approach to design a bunch compressor chicane suitable for the multi-TeV compact linear collider (CLIC). Based on analytical equations and beam dynamics simulations, we discuss how the influence of incoherent and coherent synchrotron radiation on the transverse beam emittance depends on chicane and electron beam parameters. The optimization of the bunch compressor layout and the electron beam parameters results in two different options which preserve the emittance to well within the specifications

Characterization of the Goubau line for testing beam diagnostic instruments

One of the main characteristics of the Goubau line is that it supports a low-loss, non-radiated surface wave guided by a dielectric-coated metal wire. The dominant mode of the surface wave along the Goubau line is a TM01 mode, which resembles the pattern of the electromagnetic fields induced in the metallic beam pipe when the charged particle beam passes through it. Therefore, the Goubau line can be used for the preliminary bench test and performance optimization of the beam diagnostic instruments without requiring charged particle beams from the accelerators. In this paper, we discuss the basic properties of the Goubau line for testing beam diagnostic instruments and present the initial test results for button-type beam position monitors (BPMs). The experimental results are consistent with the theoretical estimations, which indicates that Goubau line allows effective testing of beam diagnostic equipment

Insulin action on glucose and protein metabolism during L-carnitine supplementation in maintenance haemodialysis patients.

BACKGROUND: Impaired protein anabolism and insulin resistance are characteristic features of maintenance haemodialysis patients. We have used a randomised, matched-paired, double-blind, placebo-controlled experimental design to determine the capability of intravenous L-carnitine supplementation to modify insulin resistance and protein catabolism in non-diabetic patients with end-stage renal disease (ESRD) undergoing chronic haemodialysis treatment. METHODS: L-carnitine (20 mg x kg(-1)) (n = 9) or placebo (n = 10) were given intravenously at the end of seven consecutive dialysis sessions. Whole-body protein and glucose metabolism were assessed on interdialytic days by the L[1-(13)C]leucine and the [2,2-(2)H(2)]glucose kinetic models in the postabsorptive state and during euglicemic hyperinsulinemic clamp studies at baseline and at the end of the treatment period. RESULTS: L-carnitine supplementation was associated with lower (P < 0.05) rates of leucine oxidation (-11 +/- 12%) and appearance from proteolysis (-6 +/- 2%) during the clamp studies than after placebo supplementation. The rates of glucose appearance in the postabsorptive state did not change significantly in the patients receiving L-carnitine treatment. Insulin-mediated glucose disappearance was improved by L-carnitine only in those patients (n = 5) (+18 +/- 3%, P < 0.05 vs placebo group, n = 5) with greater baseline insulin resistance, selected according to the median value of insulin sensitivity before treatment. CONCLUSIONS: L-carnitine supplementation was associated with protein-sparing effects in maintenance haemodialysis patients during hyperinsulinemia