Gamma Transition Jump for PS2

The PS2, which is proposed as a replacement for the existing ~50-year old PS accelerator, is presently considered to be a normal conducting synchrotron with an injection kinetic energy of 4 GeV and a maximum energy of 50 GeV. One of the possible lattices (FODO option) foresees crossing of transition energy near 10 GeV. Since the phase-slip-factor $\eta$ becomes very small near transition energy, many intensity dependent effects can take place in both longitudinal and transverse planes. The aim of the present paper is on the one hand to scale the gamma transition jump, used since 1973 in the PS, to the projected PS2 and on the other hand based on these results the analysis of the implementation and feasibility of a gamma transition jump scheme in a conventional FODO lattice

The Use of rf-Knockout for Determination of the Characteristics of the Transverse Coherent Instability of an Intense Beam

The response of an intense beam of interacting particles to a deflecting rf-signal is computed theoretically and shown to be closely related to transverse coherent beam stability. It is shown that the beam response to sinusoidal excitation provides a direct measure of the stability of beam modes for given machine conditions (beam intensity, octupole current, sextupole current, momentum spread, etc.). This measurement includes the properties of the beam surroundings as well as the frequency spread effective for Landau damping. Since it is generally difficult to evaluate theoretically the wall and beam properties that enter into stability calculations, the information which can be obtained from rf excitation experiments should be very valuable; especially in devising practical procedures for reducing the severity of coherent transverse instabilities

On the Optimum Dispersion of a Storage Ring for Electron Cooling with High Space Charge

With the intense electron beams used for cooling, matching of the ion and electron velocity over the largest possible fraction of the beam profile becomes important. In this situation, a finite dispersion from the ring in the cooling section can lead to an appreciable gain in the transverse cooling speed. Based on a simple model of the cooling force, an expression for the "optimum" dispersion as a function of the electron beam intensity, the momentum spread and other properties of the ion beam will be derived. This simple theory will be compared to measurements made on the Low Energy Ion Ring (LEIR) at CERN during 1997

Stability of cooled beams

Because of their high density together with extremely small spreads in betatron frequency and momentum, cooled beams are very vulnerable to incoherent and coherent space-charge effects and instabilities. Moreover, the cooling system itself, i.e. the electron beam in the case of e-cooling, presents large linear and non-linear 'impedances' to the circulating ion beam, in addition to the usual beam-environment coupling impedances of the storage ring. Beam blow-up and losses, attributed to such effects, have been observed in virtually all the existing electron cooling rings. The adverse effects seem to be more pronounced in those rings, like CELSIUS, that are equipped with a cooler capable of reaching the presently highest energy (100 to 300 keV electrons corresponding to 180 to 560 MeV protons). The stability conditions will be revisited with emphasis on the experience gained at LEAR. It will be argued that for all present coolers, three conditions are necessary (although probably not sufficient) for the stability of intense cold beams: (i) operation below transition energy, (ii) active damping to counteract coherent instability, and (iii) careful control of the e-beam neutralisation. An extrapolation to the future 'medium energy coolers', planned to work for (anti)protons of several GeV, will also be attempted

A more sustainable and highly practicable synthesis of aliphatic isocyanides

Synthesis protocols to convert N-formamides into isocyanides using three different dehydration reagents (i.e. p-toluenesulfonyl chloride (p-TsCl), phosphoryl trichloride (POCl3) and the combination of triphenylphosphane (PPh3) and iodine) were investigated and optimized, while considering the principles of green chemistry. Comparison of the yield and the E-factors of the different synthesis procedures revealed that, in contrast to the typically applied POCl3 or phosgene derivatives, p-TsCl was the reagent of choice for non sterically demanding aliphatic mono- or di-N-formamides (yields up to 98% and lowest E-factor 6.45). Apart from a significantly reduced E-factor, p-TsCl is cheap, offers a simplified reaction protocol and work-up, and is less toxic compared to other dehydration reagents. Thus, this procedure offers easier and greener access to aliphatic isocyanide functionalities

Electron cooling of PB54+^{54+} ions in the low energy ion ring (LEIR)

For the preparation of dense bunches of lead ions for the LHC, electron cooling will be essential for accumula tion in a storage ring at 4.2 MeV/u. Tests have been carried out on the LEAR ring (renamed LEIR for Low Energy Ion Ring) in order to determine the optimum parameters for a future state-of-the-art electron cooling device which would be able to cool linac pulses of lead ions in less than 100 ms. The experiments focused on the generation of a stable high intensity electron beam that is needed to free space in both longitudinal and transverse phase space for incoming pulses. Investigations on the ion beam lifetime in the presence of the electron beam and on the dependency of the cooling times on the optical settings of the storage ring will also be discussed. This paper concentrates on the cooling aspects with the multiturn injection, vacuum, and high intensity aspects discussed in a companion paper at this conference

The production of dense lead-ion beams for the CERN LHC

To reach the design luminosity for lead-ions in the LHC, the present Low Energy Antiproton Ring (LEAR) has to be converted into a Low Energy Ion Ring (LEIR). Since the present ECR lead-ion source does not provide sufficient intensity, the main goal of LEIR is to act as a low-energy (4.2MeV/u) accumulator where the ion beam is stacked and cooled (with the help of an electron-cooler) to reach the required intensity and emittances. An experimental program has been carried out at LEAR in recent years in order to test the cooling and stacking process with the present electron-cooler. A variety of results have been reported at previous conferences. This paper will focus on the electron cooling aspects resulting from the afore mentioned experiments. Taking into account the experienc

Experimental investigation of electron cooling and stacking of lead ions in a low energy accumulation ring

This report gives the results of a programme of experimental investigations, which were carried out to test stacking of lead ions in a storage ring (the former Low Energy Antiproton Ring, LEAR) at 4.2 MeV per nucleon. The motivation was to demonstrate the feasibility of gaining the large factor in the phase-space density required for injection into the LHC. In the first part of the report, the layout of the experiments is described, the choice of the parameters of the electron cooling system used for stacking is reported and the multi-turn injection using horizontal- and longitudinal- (and in the final project also vertical-) phase space is discussed. In the second part the experimental results are presented. Factors of vital importance are the stacking efficiency, the beam life-time and the cooling time of the ions. The beam decay owing to charge exchange with the residual gas and to recombination by the capture of cooling electrons was intensively studied. Beam instabilities and space-charge effects in the ion beam turned out to be additional, although less serious, limitations of the accumulation rate. The cooling speed as a function of cooler and storage-ring properties was investigated over a wide range of parameters. Among the 'surprises' encountered are an anomalously fast recombination rate for certain ion charge states (Pb53+), a strong dependence of the cooling time on the dispersion function of the storage ring, and an intensity-dependent outgassing of equipment in the vacuum chamber. After a careful choice of parameters and antidotes, an overall factor of 120 in intensity could be gained, by multi-turn injection and stacking for 4 s. The intensity obtained ($6 x 10^8$ ions with a length corresponding to four LHC bunches) is only a factor of two short of the LHC requirement, and the stacking time (4 s instead of 2 s foreseen for filling each LHC ring in 8 min) is another factor of two off

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.