The AMS-02 Time of Flight System. Final Design

The AMS-02 detector is a superconducting magnetic spectrometer that will operate on the International Space Station. The time of flight (TOF) system of AMS-02 is composed by four scintillator planes with 8, 8, 10, 8 counters each, read at both ends by a total of 144 phototubes. This paper describes the new design, the expected performances, and shows preliminary results of the ion beam test carried on at CERN on October 2002.Comment: 4 pages, 6 EPS figures. Proc. of the 28th ICRC (2003

Properties of recent IBAD-MOCVD Coated Conductors relevant to their high field, low temperature magnet use

BaZrO3 (BZO) nanorods are now incorporated into production IBAD-MOCVD coated conductors. Here we compare several examples of both BZO-free and BZO-containing coated conductors using critical current (Ic) characterizations at 4.2 K over their full angular range up to fields of 31 T. We find that BZO nanorods do not produce any c-axis distortion of the critical current density Jc(theta) curve at 4.2 K at any field, but also that pinning is nevertheless strongly enhanced compared to the non-BZO conductors. We also find that the tendency of the ab-plane Jc(theta) peak to become cusp-like is moderated by BZO and we define a new figure of merit that may be helpful for magnet design - the OADI (Off-Axis Double Ic), which clearly shows that BZO broadens the ab-plane peak and thus raises Jc 5-30{\deg} away from the tape plane, where the most critical approach to Ic occurs in many coil designs. We describe some experimental procedures that may make critical current Ic tests of these very high current tapes more tractable at 4.2 K, where Ic exceeds 1000 A even for 4 mm wide tape with only 1 micron thickness of superconductor. A positive conclusion is that BZO is very beneficial for the Jc characteristics at 4.2 K, just as it is at higher temperatures, where the correlated c-axis pinning effects of the nanorods are much more obvious

The AMS-02 Time of Flight System

The Time-of-Flight (TOF) system of the AMS detector gives the fast trigger to the read out electronics and measures velocity, direction and charge of the crossing particles. The first version of the detector (called AMS-01) has flown in 1998 aboard of the shuttle Discovery for a 10 days test mission, and collected about $10^8$ events. The new version (called AMS-02) will be installed on the International Space Station and will operate for at least three years, collecting roughly $10^{10}$ Cosmic Ray (CR) particles. The TOF system of AMS-01 successfully operated during the test mission, obtaining a time resolution of 120 ps for protons and better for other CR ions. The TOF system of AMS-02 will be different due to the strong fringing magnetic field and weight constraintsComment: 6 pages, 7 figures. Talk given at the ``First International Conference on Particle and Fundamental Physics in Space'', La Biodola, Isola d'Elba (Italy), 14 -- 19 May 2002. To be published by Nuclear Physics B - Proceedings Supplement. Sep. 13, 2002: added "Conclusion" sectio

A note on Bayesian hypothesis testing for the scalar skew-normal distribution

The skew-normal distribution is a class of densities that preserves some useful properties of the normal distribution while allowing a shape parameter to account for skewness. It has various remarkable properties in terms of mathematical tractability and turned out to be quite useful in modelling real data. However from an inferential point of view its use gives raise to many difficulties, that are intrinsically tied with the shape of the likelihood function. This fact suggests to solve the problem by calibrating the likelihood with a weight function, and perhaps the most intuitive calibration can be obtained in the Bayesian framework, where the prior distribution plays naturally the role of the weight function. Here we consider in details the problem of testing normality in the general skew-normal model, and solve it by means of different tools for hypothesis testing in the Bayesian framework, namely the Bayes factor and the Jeffreys divergence, pointing out benefits and problems of both approaches