摘要:

In order to enhance the proton fraction in hydrogen ion beams, a high magnetic field, large‐volume magnetic multipole ion source has been designed and tested. The plasma source is made of a water‐cooled rectangular copper chamber, which is surrounded by a set of mild steel strips and samarium–cobalt magnets arranged in a continuous line‐cusp geometry. The magnetic field at the inner wall surface is 2.7 kG. This strong magnetic field enables us to enlarge the chamber volume without increasing the ion loss area. Large plasma volume and small ion loss area increase the ion confinement time and enhance the proton yield. The proton fraction in the beams, as measured by both a magnetic momentum mass analyzer and a optical spectrometer, is found to be more than 90% at an ion beam current of 28 A ( j=250 mA/cm2). This source is also operated with a weak magnetic field (∼0.6 kG) by replacing the samarium–cobalt magnets with AlNiCo magnet, in which case the proton fraction decreases to 80%. These experimental values are in good agreement with the values predicted by a simple scaling equation of the proton ratio on the plasma volume and the ion loss area.

ISSN:0034-6748    

DOI:10.1063/1.1137577

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Maintaining the proper low work function surface in steady‐state high‐current‐density negative ion sources is difficult, due to intense ion bombardment of the surface. Experiments were performed in which liquid cesium was forced through a porous molybdenum converter in order to obtain a low work function, while at the same time allowing the surface to be cooled. In a small steady‐state hollow cathode discharge source, the H−yield from a porous molybdenum converter was five fold higher than from a solid molybdenum converter which relied on the conventional method of cesium coverage by vapor deposition.

ISSN:0034-6748    

DOI:10.1063/1.1137596

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Diffusion of a low‐pressure (10−2Torr) hollow‐cathode discharge through an anode screen produces a linear, homogeneous, and quiescent plasma column (14 mm in diameter, 80 cm in length) in a strong magnetic field (max 3 kG). Electron temperatures and densities in this plasma, as measured by Langmuir probe and microwave cavity perturbation techniques are, respectively, in the ranges of 0.3–1.2 eV and 109–1011cm−3. Plasma noise fluctuations (e&bartil;fl/kBTe) at the center of the plasma are about 3%.

ISSN:0034-6748    

DOI:10.1063/1.1137573

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A time‐resolving grazing incidence spectrograph based on an image intensified photodiode array detector has been constructed and has demonstrated its utility as a fusion plasma diagnostic. The total wavelength coverage is 15–360 A˚ with 0.7 A˚ resolution (line profile FWHM); portions of this range may be observed during a single plasma discharge with a bandwidth of ∼40 A˚ when the detector is centered at 40 A˚ and ∼80 A˚ with it centered at 200 A˚. Integration times from 5.4 to 13.1 ms are available when the entire photodiode array is read out; integration times as short as 1 ms can be obtained for a few lines of interest through the readout of selected photodiodes. The spectrograph has been radiometrically calibrated over the 60‐ to 360‐A˚ range at the NBS SURF II electron storage ring and is currently in operation on the Princeton Large Torus (PLT) tokamak.

ISSN:0034-6748    

DOI:10.1063/1.1137576

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A flash x‐ray source has been fabricated to examine the plasma‐driven shutter for the Nova Fusion Laser System at the Lawrence Livermore National Laboratory. This source has a 20‐ns pulse width and 1.5‐ and 4.5‐keV x rays. It has been used to characterize plasma moving at 1–5 cm/&mgr;s with areal densities down to 0.1 mg/cm2and a spatial resolution of 2.5 &mgr;m. By using this x‐ray source to diagnose the Nova plasma shutter, the authors were able to discover and cure sources of plasma nonuniformity and empirically select the foil dimensions and the current required for Nova.

ISSN:0034-6748    

DOI:10.1063/1.1137578

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The preparation of filters and fluorescence of high oxygen content (53%) for low‐energy x‐ray measurements is described. The thin films of high oxygen content were fabricated from a 50:50 wt. % mixture of CelconTMand DelrinTM. Thermal analysis data on all the materials investigated are also presented.

ISSN:0034-6748    

DOI:10.1063/1.1137586

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A simple device has been developed to load thin (25 &mgr;m in diameter) wires in vacuum for an exploding wire plasma system. Wires may be loaded with high reliability, straight, and accurately positioned. An improvement in the reproducibility of the wire explosion results and is attributed to the ability to repeatedly form the electrical contacts between wire and electrodes.

ISSN:0034-6748    

DOI:10.1063/1.1137587

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A 200‐kV, 200‐mA deuterium ion accelerator has been developed to simulate the operation of an intense neutron source for use in cancer therapy. The thin‐film ScD2target for the neutron source is supported on a water‐cooled copper substrate designed to dissipate 40 MW/m2at a surface temperature of 450 °C. This paper describes the theoretical and experimental analysis of the target and the postmortem analysis of a target after 140 h of operation at power densities exceeding 40 MW/m2. Cooling channel erosion due to nucleate boiling of the cooling water was shown to be the life‐limiting feature of the target design.

ISSN:0034-6748    

DOI:10.1063/1.1137588

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A diagnostic system is described with which we obtain a sequence of six pictures (interferograms or shadowgrams) of the plasma produced by the iodine laser on solid targets. The system consists of a synchronously pumped dye laser amplified in dye cells pumped by an excimer laser. It delivers a pulse with an energy of 500  &mgr;J and a length of 3 ps at a wavelength of 580 nm that is highly synchronous with the iodine pulse.

ISSN:0034-6748    

DOI:10.1063/1.1137589

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A few mJ of KrF excimer laser radiation have been used to initiate multichannel breakdown in a low‐inductance gas‐insulated rail‐gap switch. The switch, which contains two uniform field electrodes, has been operated in a pulse‐charged voltage range of 30–130 kV and has demonstrated jitters as low as 100 ps. A very simple trigger device which incorporates the important features of laser triggering but which uses incoherent UV radiation produced in a corona discharge has also resulted in low jitter, multichannel switch performance.

ISSN:0034-6748    

DOI:10.1063/1.1137590

出版商:AIP    

年代:1984

数据来源: AIP