Transfer Line Studies from LINAC4 to the PS Booster: Green Field Option

Linac4 is a normal conducting H- linac, which is currently under study at CERN as upgrade to the present LHC injectors chain in view of intensifying the proton flux available for the CERN accelerator complex and eventually attain LHC ultimate luminosity goals. The new linac is designed to accelerate a 65 mA H- ion beam from 45 keV up to 160 MeV for charge-exchange injection into the CERN Proton Synchrotron Booster, thus overcoming the space charge limitations of the present injection mechanism at 50 MeV, which represent the main obstacle to obtaining higher beam brightness into the PS. A transfer line is being planned to transport the beam from the end of Linac4 to the PSB: a solution corresponding to a siting of the linac in the existing PS South Hall was initially studied [1] but later discarded in favour of a new "green field" arrangement of a whole complex of new machines (including the SPL and PS2) at CERN. The present note outlines this latest layout and presents the results of the relative beam dynamics studies

Study of a spectrometer line for the Linac4 diagnostics movable bench

movable diagnostics bench is currently being designed as part of the Linac4 commissioning plan to characterise the H-beam at the exit of each DTL tank. A spectrometer line has been proposed for installation on the bench to allow performing measurements of the beam energy spread with a slit/dipole/monitor technique. A layout for this diagnostics line is here proposed together with the results of beam dynamics studies to evaluate the resolution achievable and the measurement reach

Transfer Line Studies from LINAC4 to the PS Booster: "South Hall" Option

Linac4 is a new normal conducting H- linac, which is currently under study at CERN as upgrade to the present LHC injectors chain in view of intensifying the proton flux available for the CERN accelerator complex and eventually attain LHC ultimate luminosity goals. The new linac is designed to accelerate a 65 mA H- ion beam from 3 MeV up to 160 MeV for charge-exchange injection into the CERN Proton Synchrotron Booster, thus overcoming the space charge limitations of the present injection mechanism at 50 MeV, which represent the main obstacle to obtaining higher beam brightness into the PS. A new transfer line is also being planned to transport the beam from the end of Linac4 to the PSB and the present paper outlines one of the proposed layouts and gives the status of the beam dynamics studies for this solution

Updated layout of the LINAC4 transfer line to the PS Booster (Green Field Option)

At the time of defining the site of Linac4 and its integration in the complex of existing infrastructure at CERN (together with the plans for a future Superconducting Proton Linac), a series of radiation protection issues emerged that have since prompted a revision of the Linac4 to PSB transfer line layout, as was described in the document ABâNoteâ2007â037. For radiological safety reasons the distance between the planned SPL tunnel and the basement of building 513 had to be increased, and this led to the decision to lower the Linac4 machine by 2.5m. A vertical ramp was consequently introduced in the transfer line to raise the beam at the same level of LINAC2/PSB for connection to the existing transfer line. A series of error study runs has been carried out on the modified layout to have an estimate of the losses induced by quadrupole alignment and field errors. The two worst cases of each error family have been used as case studies to test the efficiency of possible steering strategies in minimizing beam losses and machine activation. The new layout and beam dynamics issues plus the results of the error and steering studies are discussed in this note

Once daily nebulized beclomethasone is effective in maintaining pulmonary function and improving symptoms in asthmatic children

Background and Aim. Compliance with long-term inhaled therapy in asthma is often poor, but it is likely to be improved with a simplified administration, once daily.The present study was designed to assess whether, in childhood asthma, a single dose of nebulized beclomethasone dipropionate once daily was as effective and safe as the same total daily dose administered twice daily. Methods. Asthmatic children, not treated with inhaled steroids for at least a month preceding the study and using short-acting bronchodilators more than once a week were enrolled in a double-blind, double dummy, randomised, multicentric study. After a two week run-in period on nebulised twice daily 400 mcg beclomethasone dipropionate, patients were randomly assigned to twelve weeks of treatment with 800 mcg nebulised beclomethasone dipropionate daily, either in single dose (o.d. group) or divided into two 400 mcg doses (b.i.d. group). Results. 65 children (mean age 8.6 years, mean FEV1 81% of predicted), were valuable for intention to treat. During the run-in period, a significant improvement in FEV1, FVC, morning and evening PEF values and clinical scores was observed. Children then entered the randomised trial: 32 were included in the o.d. group and 33 in the b.i.d. group. During the twelve week treatment period, the observed improvement in pulmonary function parameters was maintained in both treatment groups. Morning and evening PEF showed a progressive slight increase as well as PEF diurnal variability showed a progressive reduction in the two treatment groups during the whole study period without reaching statistical significance. Moreover, in both treatment groups a similar progressive increase in symptom free nights and days and in the percentage of children achieving total asthma symptoms control was detected. Finally, no significant changes in urinary cortisol/creatinine ratio were observed throughout the study period and between groups. Conclusions. A daily dose of 800 mcg of beclomethasone, administered for twelve weeks with a nebuliser either once or twice daily provide similar efficacy in maintaining pulmonary function and symptoms of asthmatic children, with a good tolerability profile

Monitoring heavy-ion beam losses in the LHC

The LHC beam loss monitor (BLM) system, primarily designed for proton operation, will survey particle losses and dump the beam if the loss rate exceeds a threshold expected to induce magnet quenches. Simulations of beam losses in the full magnet geometry allow us to compare the response of the BLMs to ion and proton losses and establish preliminary loss thresholds for quenches. Further simulations of beam losses caused by collimation and electromagnetic interactions peculiar to heavy ion collisions determine the positions of extra BLMs needed for ion operation in the LHC

Beam Loss Monitors for Heavy Ion Operation

The performance of the LHC as a heavy-ion collider is expected to be limited by a variety of beam loss mechanisms that are non-existent, or substantially different, in the case of protons. Among these are ultra-peripheral interactions of the colliding beams and the collimation inefficiency. Loss patterns are different and require additional installations of beam loss monitors. Further, the relation between energy deposition in superconducting magnet coils and the loss monitor signals has to be reassessed for heavy ions in order to determine the thresholds for dumping beams

Studies on combined momentum and betatron cleaning in the LHC

Collimation and halo cleaning for the LHC beams are performed separately for betatron and momentum losses, requiring two dedicated insertions for collimation. Betatron cleaning is performed in IR7 while momentum cleaning is performed in IR3. A study has been performed to evaluate the performance reach for a combined betatron and momentum cleaning system in IR3. The results are presented

Accelerator physics concept for upgraded LHC collimation performance

The LHC collimation system is implemented in phases, in view of the required extrapolation by 2-3 orders of magnitude beyond Tevatron and HERA experience in stored energy. All available simulations predict that the LHC proton beam intensity with the "Phase I" collimation system may be limited by the impedance of the collimators or cleaning efficiency. Maximum efficiency requires collimator materials very close to the beam, generating the dominant resistive wall impedance in the LHC. Above a certain intensity the beam is unstable. On the other hand, even if collimators are set very close to the beam, the achievable cleaning efficiency is predicted to be inadequate, requiring either beam stability beyond specifications or reduced intensity. The accelerator physics concept for upgrading cleaning efficiency, for both proton and heavy ion beams, and reducing collimator-related impedance is described. Besides the "Phase II" secondary collimators, new collimators are required in a few super-conducting regions