Prototype Undulator Research Articles

Spectral properties of a tapered gap hard x-ray undulator

A tapered undulator, in which the entrance and exit magnetic gaps are different, will show an increase in the energy width of the harmonics compared to the nontapered case. This increase can occur without substantial broadening in the collimation of the undulator radiation. We present the spectral properties measured for a tapered 3.3-cm period prototype undulator of the Advanced Photon Source at the Cornell High Energy Synchrotron Source. The width of the on-axis first harmonic at 6.9 keV increased from 0.32 to 0.66 keV for a gap tapering of 12%. Minimal angular broadening in the first harmonic x rays was detected and measurements of off-axis radiation were also performed. The results are found to be in good agreement with model calculations.

High heat load performance of an inclined-crystal monochromator with liquid gallium cooling on the CHESS-ANL undulator

Results for the performance of a novel double crystal monochromator subjected to high heat loads from an APS prototype undulator at the Cornell High Energy Synchrotron Source (CHESS) are presented. The monochromator was designed to achieve symmetric diffraction from asymmetric planes to spread out the beam footprint thereby lowering the incident power density. Both crystals had (111) oriented surfaces and were arranged such that the beam was diffracted from the (11{bar 1}) planes at 5 KeV. Rocking curves with minimal distortion were obtained at a ring electron current of 96 mA. This corresponded to 370 Watts total power and an peak power density of 48 Watts/mm{sup 2} normal to the incident beam. These results are compared to data obtained from the same crystals in the standard geometry (diffracting planes parallel to surface). The footprint area in the inclined case was three times that of the standard case. We also obtained rocking curve data for the {l_brace}333{r_brace} reflection at 15 KeV for both standard and inclined cases, and these data also showed a minimal distortion for the inclined case. In addition, thermal data were obtained via infrared pyrometry. Not only the diffraction data but also the thermal data revealed a dramaticallymore » improved performance for the inclined crystal case.« less

Microundulator scheme with redistribution of the external longitudinal magnetic field

Abstract A new undulator scheme was investigated which appeared to be perspective for the short period designs. A high current coil is used to provide the strong longitudinal magnetic field over the total undulator volume. A set of steel blocks inserted into the core area causes redistribution of this magnetic flux providing periodically alternating transverse field components. A new element of the scheme is an additional set of permanent magnet blocks placed between the steel undulator pole blocks. Magnetic field measurements made with an undulator prototype model have shown that the transverse field component can be enhanced up to a level comparable with the primary longitudinal magnetic field.

SPring-8 prototype undulator

An undulator of wedged-pole-hybrid type was constructed as a prototype undulator for the SPring-8. This device has 33 mm magnetic period, 123 magnetic poles, and generates 5.87 kG peak magnetic field at the minimum gap position (13.5 mm). The magnetic field measurements were performed on this undulator. By using these data, expected undulator radiation intensity was computed including the effect of magnetic field error. The reductions of peak intensity due to the field error were observed for higher harmonics.

Prototype photon position monitors for undulator beams at the Advanced Light Source

Design criteria are described, and test results are presented, for prototype undulator beam position monitors at the Advanced Light Source (ALS). The design is based on monitors presently in use at the National Synchrotron Light Source, Brookhaven National Laboratory, with modifications to account for the widely varying and large K values of the undulators to be installed at the ALS. In particular, we have modified the design to simplify the thermal engineering and we have explored techniques to suppress the response of the monitors to soft photons, below 100 eV, so that the beam position can be determined by measuring the higher energy photons which are better collimated.

X-Ray Fluorescence Microprobe Imaging with Undulator Radiation

AbstractSynchrotron x-ray fluorescence experiments were performed using a prototype undulator for the Advanced Photon Source installed on the CESR storage ring at Cornell University during a run in May, 1988. Fluorescence spectra were collected from a number of standard references and unknowns. Thick target minimum detectable limits (MDL) were about a factor of two higher than those obtained using white bending magnet radiation at the NSLS. The higher MDLs could be due to lower polarization and/or imperfect alignment of the Si(Li) detector. Thin target MDLs were about 10 times lower than the NSLS since the undulator produced a usable spot size which was also 10 times smaller. Several one dimensional multi-elemental scans and two dimensional images were made with 10 μm resolution and 30 ppm MDL. These experiments demonstrate that undulators on the proposed Advanced Photon Source will be ideal for a trace element x-ray fluorescence microprobe with excellent elemental sensitivity and spatial resolution.