摘要:

An RF driven H−source has been developed at LBL for use in the Superconducting Super Collider (SSC). To date, an H−current of ∼40 mA can be obtained from a 5.6‐cm‐diameter aperture with the source operated at a pressure of about 12 mTorr and 50 kW of RF power. Attempts have been made to enhance the H−beam current by introducing a small quantity of cesium vapor into the source chamber. It is found that the H−output current can be increased by a factor larger than three if some cesium is applied in the collar around the exit aperture.

ISSN:0094-243X    

DOI:10.1063/1.44798

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this paper, we will present the initial results of our experiments designed to characterize an RF‐driven, multicusp, negative‐ion source. We will describe our experiences with suppression of RF pickup in the control system signal lines. Next, the characteristics of the extracted negative‐ion beam will be described and compared with that from filament‐based sources. The beam current, electron‐to‐ion ratio, and emittance as a function of RF power will be shown. Trends will also be shown with various electron suppression collar geometries and filter‐rod field strengths. Finally, we will describe the change in beam current obtained when Cs is introduced into the plasma chamber using heated SAES dispensers.

ISSN:0094-243X    

DOI:10.1063/1.44799

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An H−current of up 30 mA has been extracted from a 1 cm2aperture in a 20 cm diameter volume source with a conical filter field. From a 9.7 cm diameter version of this source, an H−current of up to 35 mA was extracted from a 0.5 cm2aperture. In both sources, the electron‐to‐H−ratio is typically <10, and often <5.

ISSN:0094-243X    

DOI:10.1063/1.44800

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Two distinctive techniques have been developed to deliver a quantifiable dose of cesium to a volume ion source. The first method uses alkali metal dispensers in the form of thin metal wires, and the second method allows cesium to be dispensed repeatedly up to a total inventory of ∼8 g. This paper reports on the testing of these devices on two volume ion sources, and details the effects that cesium has on the extracted negative ion current and the plasma parameters. In addition, comparisons are made between the surface production model for cesium enhancement, and a volume or collisional model.

ISSN:0094-243X    

DOI:10.1063/1.44749

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We have newly designed a double plasma type negative ion source, where energy distribution of fast electrons is well controlled by changing potential difference between two chambers. With the use of this source, pure H−volume production is studied experimentally. In particular, the effect of fast electrons on H−production (i.e., energy dependence of H−production) is discussed, and preliminary results support qualitatively the two‐step process of H−production.

ISSN:0094-243X    

DOI:10.1063/1.44750

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

At the University of California, Irvine (UCI), we have been studying the production of intense H−beams using pulse power techniques for the past 7 years. Recently, we have developed diodes similar to the coaxial design of the Lebedev Physical Institute, Moscow, where current densities of up to 200 A/cm2were reported using nuclear activation of a carbon target. In experiments at UCI using the machine APEX, a 1 MV, 50 ns, 7 &OHgr; pulseline, and the coaxial diode geometry, current densities of up to 35 A/cm2from a passive polyethylene cathode loaded with TiH2have been measured using a pinhole camera and CR‐39 track recording plastic. We have also begun work on a planar diode which can generate a directed beam of H−ions. The cathode also uses TiH2loading of a polyethylene substrate and the APEX has been modified to include an external LC circuit which can generate a bipolar, 125 kV, 1 &mgr;s duration prepulse (similar prepulse characteristic as in the Lebedev Institute experiments cited above) for plasma production.

ISSN:0094-243X    

DOI:10.1063/1.44751

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Theoretical and experimental studies of the cesium influence on negative hydrogen ion emission from a reflection‐type source have been carried out. It is shown that as the cesium vapor is added to discharge, the processes occurring on the cesiated surface of the discharge chamber give the main contribution in H−ion production.

ISSN:0094-243X    

DOI:10.1063/1.44752

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A BNL‐type toroidal H−source with circular permanent magnet cusps has been designed and tested. The volume of the plasma chamber is 452 cm3. The source plasma is created by a discharge initiated from a 1 mm diameter hot tungsten filament. The discharge was operated in a pulsed mode with a maximum pulse length of 300 &mgr;sec, and a maximum discharge voltage of 200 V. For these tests, the source body was biased in the range of 1–10 kV. A permanent magnet mass filter was used to separate the extracted H−ions from the electrons. We have observed a maximum current density of 16 mA/cm2with an e/H−ratio of 16 when the operation conditions were as follows; an arc voltage of 190 V, 60 A filament current, and 10 kV extraction. The source pressure at the maximum output was estimated to be 8.2 mTorr.

ISSN:0094-243X    

DOI:10.1063/1.44753

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The Superconducting Super Collider (SSC) ion source is required to provide a 35 kV, 30 mA H−beam, with a normalized rms emittance (&egr;n‐rms) of less than 0.18 &pgr; mm‐mrad and a pulse width of 7–35 &mgr;s at a 10 Hz repetition rate. An RF‐driven volume source is chosen for the initial commissioning of the SSC linear accelerator (LINAC). An extensive experimental program has been under way to characterize the SSC volume ion source. We have achieved &egr;n‐rmsas low as 0.06 &pgr; mm‐mrad with the RF volume source while meeting all other SSC ion source operating requirements. The available experimental results pertinent to the performance of the SSC RF volume ion source will be discussed.

ISSN:0094-243X    

DOI:10.1063/1.44754

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new, large, hybrid volume negative ion source is described. Observations of curvature andgradBprimary electron drift in the multicusp magnetic field are reported. The direction of the electron drift changes from one filament to the neighboring one, because of the change in the direction of the magnetic field. For a given discharge current the extracted negative ion current and the plasma density at the center of the extraction region are affected by the direction of the primary electron drift of the active filaments. It was shown, however, that the negative ion current is controlled by the plasma density at the center of the extraction region. A trajectory calculation, effected in the guiding center approximation, allows to estimate the average drift velocity.

ISSN:0094-243X    

DOI:10.1063/1.44755

出版商:AIP    

年代:1992

数据来源: AIP