摘要:

An electronic pepper pot has been developed at DESY for analyzing the H−beam. It consists of a number of slits in front of a harp with a high wire density. Multiplexing of the harp signals is done in the vacuum. The number of slits and the distance between the harp and the slits can be varied according to the beam parameters. The first version consists of a harp with 484 wires which are 0.1 mm wide with a spacing of 0.1 mm. They are printed on a board. The storage and readout is done using three chips in the vacuum. External transfer of the analog signals is done with a few lines. One may measure the current distribution and the emittance within one shot of the beam and is free to choose the time for the sample. This is of special interest for sources with a low repetition rate such as the HERA H−source. The present arrangement is only a first step. Further designs are discussed.  

ISSN:0034-6748    

DOI:10.1063/1.1144945

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Slit‐grid emittance measurement devices usually do not scan the beam continously but in fixed linear (x) and angular (x’) steps. Thus in an emittance measurement performed with a slit‐grid system, the beam is represented by a number of phase space boxes with a constant area or volume determined by the linear and angular resolution. Considering the emittance as the area in the two‐dimensional subspace (x,x’) covered by the beam, the quantization error and its dependence on the resolution (linear and angular) as well as the influence of the beam parameters is discussed. Measuring the very low emittance of the high efficiency source (HIEFS) proved that the quantization error can be unacceptably high (≫100%). With an optimized measuring device, the normalized emittance came down from 10−1to 3.6×10−3&pgr; mm mrad. Finally, a typical misleading result of an emittance measurement, caused by the quantization error, is presented.

ISSN:0034-6748    

DOI:10.1063/1.1144946

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The present measurement system is composed of signal preprocessors, an A/D conversion card, optical fibers, a microcomputer, and an interface. After discharge parameters of an ion source at high potential, i.e., analog signals, are preprocessed by means of LPF, amplitude limit, and normalization, they are changed into digital signals by A/D conversion. The digital signals are transferred through optical fibers to low potential, then they are gathered, processed, or stored by the microcomputer. The system can measure eight analog signals at high potential through scanning. Each measurement will take about 160 &mgr;s with a precision of ±1 LSB, i.e., ±0.4% maximum relative error at full range. Measurements of discharge parameters of the ion source at high potential were made for a steady state ion source and a high current pulse ion source successively, whose results are in good agreement with practical cases. The formation and propagation of interference and approaches of anti‐interference under high current and high pulse voltage conditions are briefly described in the present article.

ISSN:0034-6748    

DOI:10.1063/1.1144947

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We have developed a metal vapor vacuum arc ion source, which was used for film deposition. Based on this source, some experimental diagnostics of plasma parameters are presented in this paper. Characters of vacuum arc cathode spots, including number, size, motion, and lifetime, are studied using a high‐speed photograph technique. Substrate bias voltage dependence of plasma microparameters, such as electron density and electron energy, are measured by a Langmuir probe measurement system. In conclusion, some discussion of experimental results are also presented.

ISSN:0034-6748    

DOI:10.1063/1.1144948

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A H2/Ar cascaded arc plasma source has been experimentally characterized by determination of the efficiency, the electric field, and the pressure gradient of the arc. The results show that the efficiency of a H2/Ar cascaded arc drops when the hydrogen flow rate is increased. The electron temperature in the argon cascaded arc has been derived to be in the range 9000–12 500 K. For a hydrogen arc, the mass dissociation degree of hydrogen molecules has been derived to be above 60%.

ISSN:0034-6748    

DOI:10.1063/1.1144949

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

For heating the plasma of HT‐6 Tokamak we have developed a multiampere ion source, which is able to provide positive ion current (pulsed 20 A). In this article we briefly introduce two significant studies we made while developing the big multicusp ion source. One is optimizing the pulse width of preadmission to obtain a uniform pulsed ion current; the other is making an insulating ring of two sorts of material to enhance the electrical character of the ring. Both of them made contributions to the extracted ion current.

ISSN:0034-6748    

DOI:10.1063/1.1144950

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

In this work we present a method to lengthen the operation life of ion sources, according to the peculiarities of the particle beam which is required by the user. To reach this goal we have modified Popov’s model and selected a fair variable that can be handled externally to prevent the break of the vacuum in the chamber. Our method could be applied to any kind of equipment containing an ion source, for instance, particle accelerators, ion implantors, neutron injectors, etc.

ISSN:0034-6748    

DOI:10.1063/1.1144951

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A phenomenological model is offered for the mechanism of a drastic increase in the desorption flow density of the native metal atoms under the influence of a high‐power density (∼107W/cm2) electron flux incident on the metal surface. The possibility is discussed of building an electron‐optical system capable of producing a submicron probe of a ∼107W/cm2power density.  

ISSN:0034-6748    

DOI:10.1063/1.1144952

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The major purpose of this paper is to describe that organic impurities cause harm to the arc discharge in the multiampere DuoPIGatron ion source and attempt to analyze the mechanism. Though we knew before that the existence of oil in the source is always harmful, for financial reasons, we had to use the available oil pump to pump gas. But we did not think that the oil pollution in the discharge chamber of the source could cause arc discharge failure so seriously that the source cannot operate normally. After encountering and solving the problem, we have recognized the severe action of oil pollution, and seen the damage mechanism. The up‐stream oil vapor from big pumps entered the chamber of the plasma generator. Should the parts of plasma chamber, especially, the target cathode be polluted by oil vapor, it resulted in destroying the reflected discharge in the chamber so that the stable condition of plasma, that isIig≫Iilcould not be maintained. HereIigandIilrepresent generated and lost ion current, respectively. The arc discharge died. After protecting the target cathode from oil pollution by various ways, our 15‐cm duoPIGatron can keep high performance operation for more than one year without recleaning. During this period, the arc current was larger than 300 A and the saturated ion current was above 234 mA/cm2.

ISSN:0034-6748    

DOI:10.1063/1.1144953

出版商:AIP    

年代:1994

数据来源: AIP