Stephanie Yang

Abstract:

A comprehensive thermal model of the ISIS H- ion source was produced in order to understand the thermal characteristics of the same. In normal operation, the source temperatures were monitored using thermocouples for the cathode, anode, and source body. A transient study was performed using the steady state solution as a starting point. The initial two-dimensional transient thermal modeling indicated that the surface heating during the arc on period only had time to penetrate a few millimeters into the electrode mass.

Abstract:

We present the results of a design study for the spectrograph module for KMOS - a cryogenic near-infrared multi-object spectrograph being developed as a second generation instrument for the VLT by a consortium of UK and German institutes. KMOS will consist of 24 deployable integral field units feeding three identical spectrograph units via image slicers. The spectrographs are designed to provide a resolving power greater than 3000, so as to provide adequate OH avoidance, whilst covering one of the J, H or K bands within a single exposure. We present the opto-mechanical layout of the spectrographs, together with an analysis of the impact of the image quality (and PSF uniformity) on the accuracy of sky background subtraction within each IFU's field of view.

Abstract:

We describe some of the design work behind the structural design of the NWSE spectrograph for the VLT1. In particular we consider the limitations on the instrument layout and the effect of its mechanical and thermal properties on the overall instrument performance.

Abstract:

We present a 201-MHz RF cavity design for muon cooling channels with non-stressed and pre-curved Be foils to terminate the beam apertures. The Be foils are necessary to improve the cavity shunt impedance with large beam apertures needed for accommodating large transverse size muon beams. Be is a low-Z material with good electrical and thermal properties. It presents an almost transparent window to muon beams, but terminates the RF cavity electro-magnetically. Previous designs use pre-stressed flat Be foils in order to keep cavity from detuning resulting from RF heating on the window surface. Be foils are expensive, and difficult to make under pre-stress to accommodate thermal expansion. An alternative design is to use pre-curved and non-stressed Be foils where the buckling direction is known, and frequency shifts can be properly predicted. We will present mechanical simulations of the Be window designs.

Abstract:

This report describes how one can integrate the muon absorber with the focusing coils of a SFOFO muon cooling channel [1]. The absorber material must be a low Z material that reduces the muon momentum with minimum scattering. The best materials to use for muon ionization cooling absorbers are hydrogen, helium, lithium hydride, lithium, and beryllium. Hydrogen or helium in an absorber would normally be in the liquid state, Lithium hydride, lithium, and beryllium would normally be in the solid state. This report limits the absorber materials discussed to hydrogen, helium, lithium, and beryllium. In order to achieve the same level of ionization cooling with a solid absorber as a liquid hydrogen absorber, the beta of the muon beam must be reduced more than a factor of two. This affects both the designs of the absorber and the magnet around it. Reducing the beam beta reduces the momentum acceptance of the channel. Integration of a liquid hydrogen absorber and solid absorbers with a superconducting focusing solenoid is discussed. The choice of absorber material affects the design of the superconducting focusing magnet and the superconductor that is used to generate the magnetic field.