Working group report: Collider Physics

This is summary of the activities of the working group on collider physics in the IXth Workshop on High Energy Physics Phenomenology (WHEPP-9) held at the Institute of Physics, Bhubaneswar, India in January 2006. Some of the work subsequently done on these problems by the subgroups formed during the workshop is included in this report.     

Surface ablation by excimer laser irradiation of Ti and Ti6Al4V alloy

This paper presents the surface microstructure of Ti and Ti6Al4V alloy irradiated with a high output energy XeCl ( = 308 nm) excimer laser. The treatments are carried out on both materials at two beam fluences and the effects of single- and multiple-pulse irradiation are compared. The results of the scanning electron microscopy and of the X-ray diffraction techniques suggest the possible influence of both time-behaviour and energy fluence of the laser pulse on the relative weight of the ablation rate and of the reaction product deposition rate at the sample surface.     

Solid-supported solution-phase synthesis of 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones

Starting from Boc-o-aminomethylphenylalanine, a solution-phase parallel synthesis of 2,4-substituted 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-ones is described. This heterocycle has two nitrogen functions, which are differentiated and can be selectively substituted. The sources of diversity are aldehydes for the R(1) position and carboxylic acids, sulfonyl chlorides, or isocyanates for the R(2) position. High-throughput synthesis and purification of this multistep synthetic sequence was accomplished using polymer-bound reagents and scavengers and liquid-liquid extraction protocols, and a small library of compounds was prepared. Polymer-bound cyanoborohydride was found to work well for the reductive amination. Scavenging of excess of amine was performed by polymer-bound benzaldehyde, and cyclization was performed in the presence of polymer-bound coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). After Boc-deprotection, the second nitrogen can be acylated using carboxylic acids, sulfonylated or converted to a urea. The acylation is again performed by polymer-bound EDC. Excellent yields and purities were obtained.     

Generic structure of externally driven tearing modes instabilities

A major limit to steady state and advanced high operation of tokamaks of reactor class is due to the onset of tearing modes that develop magnetic and may cause loss of energy confinement or a major disruption. Here the structure of a classical problem about the effects of external control helical fields is analysed and it is shown to offer a general paradigm of response of low order classical and neoclassical tearing modes to a wide class of external perturbations. New results of principle on the structural stability of the response model are obtained, leading to a clear interpretation of the role of “seed islands" in the onset of neo-classical tearing modes and the role of finite ion larmor radius corrections to Ohm's law. Received 12 November 2001 and Received in final form 4 January 2002     

High-efficiency clean EUV plasma source at 10–30 nm, driven by a long-pulse-width excimer laser

A long-pulse-width high-output energy (120 ns FWHM, 7 J) XeCl laser has been focused on thin tape targets (Cu and Ta) to generate more than 100-ns-long (FWHM) EUV pulses in the 10–30 nm spectral region, suitable for projection microlithography. The conversion efficiency was more than 20% over a 2π solid angle. We observed debris emission using a gated CCD camera, and measured the debris speed for different irradiation conditions. We found irradiation conditions such that the measured velocities were low enough that simple mechanical devices combined with krypton at low-pressure could efficiently stop both ionic debris and cluster debris. Our results show that a suitable combination of driving-laser characteristics, target material and thickness, environment gas and mechanical choppers can make clean and increase the power of EUV solid-target laser-plasma sources. Received: 21 October 2002 / Published online: 26 February 2003 RID="*" ID="*"Corresponding author. Fax: +39-06/9400-5334, E-mail: bollanti@frascati.enea.it     

Some design limitations for large-aperture high-energy per pulse excimer lasers

Summary Some limitation problems for gas discharge excimer lasers, when scaled to a high pulsed energy output with high repetition rate are discussed. As an example, we present some experimental results obtained with an X-ray preionized (10×10×100) cm³ active volume, low-repetition-rate-operated gas discharge XeCl laser system. ENEA student. ENEA guest.     

On the singularity of Green's tensor for a perfectly conducting semi-infinite cone

This paper is intended to clarify a misunderstanding concerningthe source singularity of the electric Green's tensor for aperfectly conducting semi-infinite cone of circular cross-section.Tai's series expansion of the Green's tensor is known to lacka singular term at the source region. Jones has reconstructedthe solution to this problem and has pointed out the differencebetween his result and that of Tai. The aim of our paper isto demonstrate that, although Jones's closed-form solution iscorrect, there is a mistake in his comparison with Tai's seriessolution. We conclude that one of the two additional singularterms that Jones claims as missing from Tai's formula must beomitted. Besides, we compare Jones's closed-form solution withSmyshlyaev's solution to the very same problem. We concludethat the magnetic field expressions given by Jones and Smyshlyaevcoincide, but a singular term is missing from Smyshlyaev's expressionfor the electric field.