Upgrade of existing injectors: the CERN PS?

Upgrade of existing injectors: the CERN PS?

Nuclear Instruments and Methods in Physics Research A 451 (2000) 154}156 Upgrade of existing injectors: the CERN PS? Vittorio Palladino* University o...

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Nuclear Instruments and Methods in Physics Research A 451 (2000) 154}156

Upgrade of existing injectors: the CERN PS? Vittorio Palladino* University of Napoli, INFN Sezione di Napoli, Napoli, Italy

Abstract The possibility of an upgraded performance of the CERN PS that would make it a suitable driver for a "rst low-intensity neutrino factory was investigated. A closer scrutiny during and immediately after the workshop concluded that the envisaged upgraded performance does not appear rooted solidly in the 40 years of running experience of the CERN PS. In addition, the CERN PS is not expected in the coming years to be available for neutrino-factory operation for more than a small fraction of its time.  2000 Published by Elsevier Science B.V. All rights reserved.

1. Introduction Recently, renewed interest in the performance of the CERN PS for neutrino physics arose for several reasons. The K2K experiment [1] in Japan is operating the "rst long-baseline conventional neutrino beam from a similar proton driver (KEK). A neutrino experiment, P313 [2], has been proposed at the CERN PS in order to test the LSND claim for electron neutrino appearance. The possibility of using the CERN PS as a driver for a neutrino factory has also recently emerged.

2. CERN PS proton economics The proposed experiment P313 [2] is based on the neutrino-event rate per proton on target (pot) and unit detector mass recorded in the 1980s by the PS180 experiment [3] at BEBC. It amounts to

* Corresponding author. Tel.: 00-41-22-767-3541; fax: 00-4122-767-3100. E-mail address: [email protected] (V. Palladino).

3.7;10\ m!! l /pot/ton. The CERN PS neutrino beam used for PS180 was a wide-band horn-focused beam with an average neutrino energy E of J about 1.5 GeV. The goal stated in P313 is the collection of 2.5;10 protons, to be able to collect more than 1 00 000 quasi-elastic m!! l events in its far detector 885 m away. Thus, a complete coverage of the LSND claim [4,5] would be possible. A careful study of the CERN PS proton yield was therefore undertaken [5,6]. It concluded that 2.3;10 pot could be reasonably provided per year and the goal of P313 could be achieved while still satisfying all other users of the CERN PS.

3. Prospects for a CERN PS upgrade The above-mentioned study used the following list of parameters. The CERN PS operates at a frequency of 0.83 Hz (1 spill in 1.2 s, if the machine is operated below 20 GeV/c). A maximum average intensity of 1.0;10 protons/s can be accelerated within the radiation hazard limits presently in force

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V. Palladino / Nuclear Instruments and Methods in Physics Research A 451 (2000) 154}156 Table 1 Present and extrapolated performance of the CERN PS Present SchoK nauer's Palmer's CERN PS proposal proposal Frequency (cycles/s) Intensity/s (protons/s) Beam energy (GeV) Total pot/year Power (GeV/s) Power (MW) Improvement factor

0.8333 1.0;10 19.2 2.3;10 1.9;10 0.031 1

1 3.7;10 26 8.3;10 9.6;10 0.153 5.0

2 2.0;10 26 4.5;10 5.2;10 0.832 27.1

at the machine. Assuming one year of operation (6800 h) at 92% e$ciency, one obtains the abovementioned "gure of 2.3;10 pot/year. Running as foreseen, at 19.2 GeV/c proton momentum, one obtains the total power in GeV/s and in MW in the "rst column of Table 1. We take as a reference this present performance level of the CERN PS and assign an improvement factor of 1. It was noticed in a recent paper of Bueno et al. [7] that this amount of protons could drive a reasonably powerful neutrino factory. If a collection of 0.08 l/pot is assumed like in Ref. [8] then the neutrino factory could store about 2.0;10 muons per year. The conclusion Bueno et al. [6,7] is that in a few years a good medium baseline (3.5 km) neutrino experiment aimed at checking the LSND claim for electron neutrino appearance could be performed by such a neutrino factory. If the CERN PS performance could be upgraded, its potential as a driver of a Neutrino factory would accordingly increase. This generated quite some interest and a few speci"c extrapolations of performance. Two of them, a bold one suggested by Palmer and a more modest one by SchoK nauer are also presented in Table 1. SchoK nauer's proposal relies on an increase of the repetition frequency to 1 Hz and a drastic increase of the intensity per unit time up to 3.7;10 protons/s. Operation of the CERN PS at 26 GeV/c would also be part of the upgrade. A factor of about "ve could thus be gained in power available for the production of muons in a neutrino factory. Palmer's proposal relies on a further increase of the repetition frequency to 2 Hz, and on an inten-

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sity per unit time larger by a factor of six. A gain factor of about 27 would follow, making the CERN PS a machine capable of almost 1 MW power. While this second extrapolation was rapidly recognised as too bold, the more modest one shown in column 2 was discussed at great length before, during and after this workshop. It would mean that a useful, though "rst-generation, neutrino factory capable of almost 10 muons per year could be driven by the CERN PS. This would be already a muon complex capable of supporting long-baseline experiments. It would be about 10 times more intense than the presently planned conventional neutrino beam from CERN to the Gran Sasso Laboratory [9].

4. Conclusions The discussion at this workshop and later in the CERN PS division, however, concluded that the more modest extrapolation was far from being proved and would require a long and di$cult machine improvement programme of uncertain outcome. In addition, it is essentially impossible to devote a large fraction of the PS operation time to this R&D programme, and later to drive a neutrino factory. The CERN PS provides protons with all CERN experimental activities: the experiments at the CERN PS, ISOLDE, the experiments at the SPS, and in the future also the LHC. Insisting on the concept of a neutrino factory driven by the CERN PS would indeed hinder a vigorous development of a muon storage-ring complex at CERN with its own dedicated powerful proton driver.

References [1] T. Hasegawa, K2K: status and prospects, presented at NuFact99, Lyon, 1999. [2] Letter of intent CERN-SPSC/97-21 (December 1997), and proposal CERN-SPSC/P313, August 1999. [3] C. Angelini, et al. (BEBC Collaboration), Phys. Lett. B 179 (1986) 307. [4] C. Athanassopoulos, et al. (LSND Collaboration), Phys. Rev. Lett. 81 (1998) 1774. [5] C. Athanassopoulos et al., Phys. Rev. C 58 (1998) 2489.

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[6] Technical Note PS/CA/Note 99-18 (1999). [7] A. Bueno, M. Campanelli, A. Rubbia, preprint hep-ph/ 0000947. [8] C.M. Ankenbrandt et al. (Muon Collider Collaboration), Phys. Rev. ST Accel. Beams 2 (1999) 081001; S. Geer, C. Johnstone, D. Neu!er, FERMILAB-PUB-99-121.

[9] G. Acquistapace et al., The CERN neutrino beam to Gran Sasso (NGS), Report CERN 98-02 and INFN/ AE-98/05; Addendum CERN SL-99-034 DI and INFN/AE-99/05.