[en] To study the effects of frequency on an electron cyclotron resonance (ECR) ion source, the LBL Advanced ECR ion source (designed to operate at 14 GHz) has been tested at 6.4, 10, and 14 GHz with one plasma chamber (ID = 6.0 cm), a permanent sextuple magnet (''closed sextuple'') with a field strength of 0.84 Tesla at the chamber wall, and no radial vacuum pumping. Pure oxygen was used as the running gas for a fair comparison. The source was tested as a single stage, as well as with cold electron injection using an electron gun in place of a conventional microwave-driven first stage. Higher frequency, with a higher axial magnetic field to ensure a closed ECR zone for electron heating, does give better performance. As demonstrated before, at each frequency electron injection led to about a factor of two increase in the high charge state oxygen beam intensity. The 14 GHz performance of the AECR source with the closed sextuple magnet was compared to the ''slotted sextuple'' (a plasma chamber with radial pumping slots of 7.0-cm dia and a weaker magnet of 0.64 Tesla at the chamber wall). Results show that a stronger sextuple magnet alone does not automatically improve the source performance

[en] The AECR source, which operates at 14 GHz, is being developed for the 88-Inch Cyclotron at Lawrence Berkeley Laboratory. The AECR has been under source development since December 1989, when the mechanical construction was completed. The first AECR beams were injected into the cyclotron in June of 1990 and since then a variety of ion species from the AECR have been accelerated. The cyclotron recently accelerated ²⁰⁹Bi³⁸⁺ to 954 MeV. An electron gun, which injects 10 to 150 eV electrons into the plasma chamber of the AECR, has been developed to increase the production of high charge state ions. With the electron gun the AECR has produced at 10 kV extraction voltage 131 eμA of O⁷⁺, 13 eμA of O⁸⁺, 17 eμA of Ar¹⁴⁺, 2.2 eμA of Kr²⁵⁺, 1 eμA of Xe³¹⁺, and 0.2 eμA of Bi³⁸⁺. The AECR was also tested as a single stage source with a coating of SiO₂ on the plasma chamber walls. This significantly improved its performance compared to no coating, but direct injection of electrons with the electron gun produced the best results. 5 refs., 6 figs., 4 tabs

[en] The installation of a second cryo panel has significantly improved the vacuum in the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The neutral pressure in the extraction region decreased from 1.2 x 10^-6 down to about 7 x 10^-7 Torr. The vacuum improvement reduces beam loss from charge changing collisions and enhances the cyclotron beam transmission, especially for the high charge state heavy ions. Tests with improved vacuum show the cyclotron transmission increased more than 50% (from 5.7% to 9.0%) for a Xe²⁷⁺ at 603 MeV, more than doubled for a Bi⁴¹⁺ beam (from 1.9% to 4.6%) at 904 MeV and tripled for a U⁴⁷⁺ beam (from 1.2% to 3.6%) at 1,115 MeV. At about 5 NeV/nucleon 92 enA (2.2 pnA) for Bi⁴¹⁺ and 14 enA (0.3 pnA) for U⁴⁷⁺ were extracted ut of the 88-Inch Cyclotron Ion beams with charge states as high as U⁶⁴⁺ have been produced by the LBNL AECR-U ion source and accelerated through the cyclotron for the first time. The beam losses for a variety of ultra high charge state ions were measured as a function of cyclotron pressure and compared with the calculations from the existing models

[en] The AECR source, which operates at 14 GHz, is being developed for the 88-Inch Cyclotron at Lawrence Berkeley Laboratory. The AECR has been under source development since December 1989, when the mechanical construction was completed. The first AECR beams were injected into the cyclotron in June of 1990 and since then a variety of ion species from the AECR have been accelerated. The cyclotron recently accelerated ²⁰⁹Bi³⁸⁺ to 954 MeV. An electron gun, which injects 10 to 150 eV electrons into the plasma chamber of the AECR, has been developed to increase the production of high charge state ions. With the electron gun the AECR has produced at 10 kV extraction voltage 131 eμA of O⁷⁺, 13 eμA of O⁸⁺, 17 eμA of Ar¹⁴⁺, 2.2 e μA of Kr²⁵⁺, 1 eμA of Xe³¹⁺, and 0.2 eμA of Bi³⁸⁺. The AECR was also tested as a single stage source with a coating of SiO₂ on the plasma chamber walls. This significantly improved its performance compared to no coating, but direct injection of electrons with the electron gun produced the best results

[en] An electron gun for the advanced electron cyclotron resonance (AECR) source has been developed to increase the production of high charge state ions. The AECR source, which operates at 14 GHz, is being developed for the 88-in. cyclotron at Lawrence Berkeley Laboratory. The electron gun injects 10 to 150 eV electrons into the plasma chamber of the AECR. With the electron gun the AECR has produced at 10 kV extraction voltage 131 e μA of O⁷⁺, 13 e μA of O⁸⁺, 17 e μA of Ar¹⁴⁺, 2.2 e μA of Kr²⁵⁺, 1 e μA of Xe³¹⁺, and 0.2 e μA of Bi³⁸⁺. The AECR was also tested as a single stage source with a coating of SiO₂ on the plasma chamber walls. This significantly improved its performance compared to no coating, but direct injection of electrons with the electron gun produced the best results

[en] The installation of a second cryo panel has significantly improved the vacuum in the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The neutral pressure in the extraction region decreased from 1.2 x 10^-6 down to about 7 x 10^-7 Torr. The vacuum improvement reduces beam loss from charge changing collisions and enhances the cyclotron beam transmission, especially for the high charge state heavy ions. Tests with improved vacuum show the cyclotron transmission increased more than 50% (from 5.7% to 9.0%) for a Xe²⁷⁺ at 603 MeV, more than doubled for a Bi⁴¹⁺ beam (from 1.9% % to 4.6%) at 904 MeV and tripled for a U⁴⁷⁺ beam (from 1.2% to 3.6%) at 1115 MeV. At about 5 MeV/nucleon 92 enA (2.2 pnA) for Bi⁴¹⁺ and 14 enA (0.3 pnA) for U⁴⁷⁺ were extracted out of the 88-Inch Cyclotron Ion beams with charge states as high as U⁶⁴⁺ have been produced by the LBNL AECR-U ion source and accelerated through the cyclotron for the first time. The beam losses for a variety of ultra high charge state ions were measured as a function of cyclotron pressure and compared with the calculations from the existing models. (authors)

[en] The Large Hadron Collider (LHC) beams are designed to have high stability and to be stored for many hours. The nominal beam intensity lifetime is expected to be of the order of 20h. The Phase II collimation system has to be able to handle particle losses in stable physics conditions at 7 TeV in order to avoid beam aborts and to allow correction of parameters and restoration to nominal conditions. Monte Carlo simulations are needed in order to evaluate the behavior of metallic high-Z collimators during operation scenarios using a realistic distribution of losses, which is a mix of the three limiting halo cases. Moreover, the consequences in the IR7 insertion of the worst (case) abnormal beam loss are evaluated. The case refers to a spontaneous trigger of the horizontal extraction kicker at top energy, when Phase II collimators are used. These studies are an important input for engineering design of the collimation Phase II system and for the evaluation of their effect on adjacent components. The goal is to build collimators that can survive the expected conditions during LHC stable physics runs, in order to avoid quenches of the SC magnets and to protect other LHC equipments.

[en] The Large Hadron Collider (LHC) collimation system is installed and commissioned in different phases, following the natural evolution of the LHC performance. To improve cleaning efficiency towards the end of the low beta squeeze at 7TeV, and in stable physics conditions, it is foreseen to complement the 30 highly robust Phase I secondary collimators with low impedance Phase II collimators. At this stage, their design is not yet finalized. Possible options include metallic collimators, graphite jaws with a movable metallic foil, or collimators with metallic rotating jaws. As part of the evaluation of the different designs, the FLUKA Monte Carlo code is extensively used for calculating energy deposition and studying material damage and activation. This report outlines the simulation approach and defines the critical quantities involved.