Overview of the recent operation of the AAC and LEAR for the low-energy antiproton physics programme

This paper reviews the recent performance of the AAC and LEAR. Activities on the AAC include the successful exploitation of a magnetic horn as an antiproton collector lens and an energy-saving mode of operation, which has been possible since 1992, when LEAR became the only client of the AAC. LEAR worked in its full momentum range between 100 MeV/c and 2 GeV/c, with perform-ance (intensities, ejection modes and spill length) exceeding the design specifications. Improvements are described, which contributed to the quality of the beam delivered to experiments. The reliability and availability of the antiproton machines are also discussed

Quantum Limits of Stochastic Cooling of a Bosonic Gas

The quantum limits of stochastic cooling of trapped atoms are studied. The energy subtraction due to the applied feedback is shown to contain an additional noise term due to atom-number fluctuations in the feedback region. This novel effect is shown to dominate the cooling efficiency near the condensation point. Furthermore, we show first results that indicate that Bose--Einstein condensation could be reached via stochastic cooling.Comment: 5 pages, 3 figures, to appear in Phys. Rev.

Measurement of the lifetime of Pb52+^{52+}, Pb53+^{53+} and Pb54+^{54+} beams at 4.2 MeV per nucleon subject to electron cooling

By measuring the lifetime of stored beams, the recombination of the ions with cooling electrons was investigated. Rates found are larger than expected for radiative electron capture and significantly higher for Pb53+ than for Pb54+ and Pb52+. These results are important for the design of the lead ion injection system for the Large Hadron Collider and for recombination theories

Proton Drivers for Neutrino Factories: The CERN Approach

The paper describes the CERN approach for a proton driver for a Neutrino Factory. Two main layouts are presented: the so-called CERN Reference Scenario, based on a 2.2 GeV linac and an alternative one, based on a 30 GeV synchrotron. Both produce bunches of 1 ns (r.m.s.) and a beam power of 4 MW

Design of a 2.2 GeV Accumulator and Compressor for a Neutrino Factory

The proton driver for a neutrino factory must provide megawatts of beam power at a few GeV, with nonosecond long bunches each containing more than 1x1012 protons. Such beam powers are within reach of a high-energy linac, but the required time structure cannot be provided without accumulation and compression. The option of a linac-based 2.2 GeV proton driver has been studied at CERN, taking into account the space charge and stability problems which make beam accumulation and bunch compression difficult at such a low-energy. A solution featuring two rings of approximately 1 km circumference has been worked out and is described in this paper. The subjects deserving further investigation are outlined

Cytoplasmic poly-GA aggregates impair nuclear import of TDP-43 in C9orf72 ALS/FTLD

A repeat expansion in the non-coding region of C9orf72 gene is the most common mutation causing frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Sense and antisense transcripts are translated into aggregating dipeptide repeat (DPR) proteins in all reading frames (poly-GA,-GP,-GR,-PA and -PR) through an unconventional mechanism. How these changes contribute to cytoplasmic mislocalization and aggregation of TDP-43 and thereby ultimately leading to neuron loss remains unclear. The repeat RNA itself and poly-GR/PR have been linked to impaired nucleocytoplasmic transport. Here, we show that compact cytoplasmic poly-GA aggregates impair nuclear import of a reporter containing the TDP-43 nuclear localization (NLS) signal. However, a reporter containing a non-classical PY-NLS was not affected. Moreover, poly-GA expression prevents TNF alpha induced nuclear translocation of p65 suggesting that poly-GA predominantly impairs theimportin-alpha/beta-dependent pathway. In neurons, prolonged poly-GA expression induces partial mislocalization of TDP-43 into cytoplasmic granules. Rerouting poly-GA to the nucleus prevented TDP-43 mislocalization, suggesting a cytoplasmic mechanism. In rescue experiments, expression of importin-alpha (KPNA3, KPNA4) or nucleoporins (NUP54, NUP62) restores the nuclear localization of the TDP reporter. Taken together, inhibition of nuclear import of TDP-43 by cytoplasmic poly-GA inclusions causally links the two main aggregating proteins in C9orf72 ALS/FTLD pathogenesis

Recent Results on Lead-Ion Accumulation in LEAR for the LHC

To prepare dense bunches of lead ions for the LHC it has been proposed to accumulate the 4.2 MeV/u linac beam in a storage ring with electron cooling. A series of experiments is being performed in the low-energy ring LEAR to test this technique. First results were already reported at the Beam Crystallisation Workshop in Erice in November 1995. Two more recent runs to complement these investigations were concerned with: further study of the beam lifetime; the dependence of the cooling time on optical settings of the storage ring and on neutralization of the electron beam; tests in view of multiturn injection. New results obtained in these two runs in December 1995 and in April 1996 will be discussed in this contribution

The antiproton decelerator (AD), a simplified antiproton source (feasibility study)

In view of a possible future physics programme concerning antihydrogen a simplified scheme for the provision of antiprotons of a few MeV has been studied. It uses the present target area and the modified Antiproton Collector (AC) in its present location. In this report all the systems are reviewed and their modifications discussed

An Antiproton Decelerator in the CERN PS Complex

The present CERN PS low-energy antiproton complex involves 4 machines to collect, cool, decelerate and supply experiments with up to 1010 antiprotons per pulse and per hour of momenta ranging from 0.1 to 2 GeV/c. In view of a possible future physics programme requiring low energy antiprotons, mainly to carry out studies on antihydrogen, a simplified scheme providing at low cost antiprotons at 100 MeV/c has been studied. It requires only one machine, the present Antiproton Collector (AC) converted into a cooler and decelerator (Antiproton Decelerator, AD) and delivering beam to experiments in the hall of the present Antiproton Accumulator Complex (AAC) [1]. This paper describes the feasibility study of such a scheme [2]

The antiproton decelerator: AD

A simplified scheme for the provision of antiprotons at 100 MeV/c based on fast extraction is described. The scheme uses the existing production target area and the modified Antiproton Collector Ring in their current location. The physics programme is largely based on capturing and storing antiprotons in Penning traps for the production and spectroscopy of antihydrogen. The machine modifications necessary to deliver batches of 1 107 /min at 100 MeV/c are described. Details of the machine layout and the experimental area in the existing AAC Hall are given