"Aggregation Bias" DOES explain the PPP puzzle

This article summarizes our views on the role of an "aggregation bias" in explaining the PPP Puzzle, in response to the several papers recently written in reaction to our initial contribution. We discuss in particular the criticisms of Imbs, Mumtaz, Ravn and Rey (2002) presented in Chen and Engel (2005). We show that their contentions are based on: (i) analytical counter-examples which are not empirically relevant; (ii) simulation results minimizing the extent of "aggregation bias"; (iii) unfounded claims on the impact of measurement errors on our results; and (iv) problematic implementation of small-sample bias corrections. We conclude, as in our original paper, that "aggregation bias" goes a long way towards explaining the PPP puzzle

Advanced target concepts for production of radioactive ions and neutrino beams

The 1-20 MW of proton beam power which modern accelerator technology put at our disposal for production of intense secondary beams presents a major technically challenge to the production targets. A conceptual design is presented for a high-power pion production target and collection system, which was originally suggested to be used as the source for the proposed CERN muon-neutrino factory. It will be shown that the major parts of this target could also serve as an efficient spallation neutron source for production of 6He and fission products in the two-step converter-target concept. The heart of the system consists of a free surface Mercury jet with a high axial velocity, which allows the heat to be carried away efficiently from the production region. For the neutrino factory the secondary pions are collected and injected into the pion decay-channel by means of a magnetic horn. For the radioactive ion-beam facility the Hg-jet is surrounded by the high-temperature ISOL production-target. The suggested mechanical layout and technical parameters of the Hg-jet, ISOL target, horn and cooling system are discussed. The critical issues are identified and a description of the R&D program designed to provide experimental proof of the principle as well as providing engineering parameters is given

The Role of Diffusion in ISOL Targets for the Production of radioactive Ions Beams

On line isotope separation techniques (ISOL) for production of ion beams of short-lived radionuclides require fast separation of nuclear reaction products from irradiated target materials followed by a transfer into an ion source. As a first step in this transport chain the release of nuclear reaction products from refractory metals has been studied systematically and will be reviewed. High-energy protons (500-1000MeV) produce a large number of radionuclides in irradiated materials via the nuclear reactions spallation, fission and fragmentation. Foils and powder of Re, W, Ta, Hf, Mo, Nb, Zr, Y, Ti and C were irradiated with protons (600-1000MeV) at the Dubna synchrocyclotron and at the CERN PS-booster to produce different nuclear reaction products. The main topic of the paper is the determination of diffusion coefficients of the nuclear reaction products in the target matrix, data evaluation and a systematic interpretation of the data. The influence of the ionic radius of the diffusing species and the lattice type of the host material used as matrix or target on the diffusion will be evaluated from these systematics. Special attention was directed to the release of group I, II and III-elements. Arrhenius plots lead to activation energies of the diffusion process

A Second Generation Radioactive Nuclear Beam Facility at CERN

The proposed Superconducting Proton Linac (SPL) at CERN would be an ideal driver for a proton-driven second-generation Radioactive Nuclear Beam facility. We propose to investigate the feasibility of constructing such a facility at CERN close to the present PS Booster ISOLDE facility. The existing ISOLDE facility would be fed with a 10 micro-amps proton beam from SPL, providing the physics community with a low-intensity experimental area. A second, new facility would be built with target stations deep underground, permitting proton beam intensities of more than 100 micro-amps. The secondary beams can be post-accelerated to 20-100 MeV/u and there will be a storage ring complex and large segmented detectors in the experimental area. Also, benefits from a muon-ion collider or from merging the ions and muons should be investigated. Since the antiproton decelerator would be nearby, the opportunities for antiprotonic radioactive atom studies should be pursued as well