摘要:

The requirements for future electron positron linear colliders are examined. It is concluded that in the energy regime approaching 10 TeV the present single pass linear collider will probably be unsatisfactory due to high backgrounds, excessive power demand or both. Energy recovery and beam neutralization as ways to avoid this hiatus are discussed.

ISSN:0094-243X    

DOI:10.1063/1.44090

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

This is the Summary Report of the ‘‘High Intensity EM Waves’’ working group at the 3rd International Workshop on Advanced Accelerator Concepts held June 14–20, 1992 in Port Jefferson, Long Island, New York. The requirements for future linear colliders with regard to microwave amplifiers is delineated in Section I along with key parameters that allow for the determination of the present status of each research effort that was discussed at the conference. The present status of amplifiers with beam energies less than 800 keV are summarized in Section II. In Section III, we summarize the status of the more non‐traditional schemes associated with the two‐beam concept, in which the energy of the microwave‐generating electron beam is much greater than 1 MeV.

ISSN:0094-243X    

DOI:10.1063/1.44097

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

X‐Band and K‐Band gyroklystrons are being evaluated for possible application to future linear colliders. So far we have examined then different two‐ and three‐cavity configurations. We have achieved a maximum peak power of 27 MW in ∼1 &mgr;s pulses at a gain of 36 dB and an efficiency exceeding 32%. The nominal parameters include a 430 kV, 150–200 A˚ beam with an average perpendicular to parallel velocity ratio near one. In this paper, we detail our progress to data and describe our plans for future experiments that should culminate in amplifier outputs in excess of 100 MW in 1 &mgr;s pulses.

ISSN:0094-243X    

DOI:10.1063/1.44102

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Relativistic gyrotrons (electron kinetic energy on the order of the rest energy or greater) differ from their weakly relativistic counterparts in two important ways: the Larmor radius is large, which puts bounds on the allowable pitch angle for a given beam tunnel radius and magnetic field, and operation at Doppler upshited frequencies, which allows for the extraction of energy from the axial motion, is feasible even in fast wave devices. Consequently, there are a number of issues that are not present at low voltage: computing the electromagnetic and AC space charge fields is not straightforward; achieving high efficiency while still maintaining the cutoff condition in the beam tunnels may be problematic, especially at cyclotron harmonics; and the use of slow wave structures to achieve very high electronic efficiency is a possibility. In this paper we consider how these issues affect modeling, and discuss the advantages and limitations of high voltage operation. We also present a specific example, the gyrotwistron, as a highly efficient device for operation in the high power regime.

ISSN:0094-243X    

DOI:10.1063/1.44062

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

At power levels exceeding the 100 MW level the spectrum of the output signal from a traveling wave tube amplifier contains a significant amount of power in frequencies other than the input frequency. The structure of the spectrum is determined by the noise in the system and the interference of the two waves bouncing due to finite reflections at the two ends of the waveguide. There are cases when the power in these selected frequencies is actually equal or even larger than in the initial frequency. Consequently, the device operates more like an oscillator than as an amplifier. In order to overcome this problem we have designed a narrow band periodic structure in which the electrons, whether they are bunched or not, can emit radiation only in a range of less than 50 MHz—in comparison to 1.5 GHz in the old structure. In this structure the group velocity is very low (&bgr;gr<0.01) and therefore the gain per unit length (for the same current) is about 5 times larger than in the previous structure. The low group velocity practically eliminates also the reflection problem since we can design the system such that by the time the first reflected wave reaches the input, the electron pulse has ended.

ISSN:0094-243X    

DOI:10.1063/1.44074

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We present a report on a program to develop a high‐power X‐band magnicon amplifier for linear accelerator applications. The goal of the program is to generate 50 MW at 11.4 GHz with 50% efficiency, using a 200 A, 500 keV electron beam produced by a cold‐cathode diode on the NRL Long‐Pulse Accelerator Facility. The initial experiment, designed to study the gain from the first (driven) deflection cavity to a second (passive) deflection cavity, is under way.

ISSN:0094-243X    

DOI:10.1063/1.44082

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Current approaches are reviewed for developing an rf source for driving the Next Linear Collider (NLC) based on various gyroresonance interactions. An alternative mechanism is described, with the potential of converting 2.85 GHz power from a SLAC klystron to output at a harmonic ranging from 11.4 to 31.4 GHz. Preliminary calculations show that this new process can enjoy high conversion efficiency, strong resilience to axial momentum spread on the beam, and weak power flow into competing modes.

ISSN:0094-243X    

DOI:10.1063/1.44036

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report on theoretical studies to demonstrate the conceptual feasibility of a high‐power sheet‐beam klystron operating at 11.4 GHz. Numerical simulations are used to investigate beam dynamics and rf issues. Specific problems with the gun design, magnetic focusing, and rf coupling at the output gaps unique to the strip beam geometry of the SBK are considered. Very high efficiencies have been calculated for several values of perveance per square beam element of the SBK. We have found that a lowg‐perveance, x‐band, sheet‐beam klystron is capable of producing over 200 MW of power at 65% efficiency, using a flat electron beam with a reasonable size of 0.4 cm×16 cm, a moderate voltage of 400 Kev, a strip gun compression ratio of 10:1, a cathode loading of 124/cm2, a uniform focusing field of 3 KG, and a double‐gap standing‐wave output cavity. With only a constant longitudinal focusing field, the calculated efficiency of the SBK is among the highest of current or proposed HPM sources. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.44049

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We propose a method to produce radiation in the centimeter‐to‐millimeter wavelength range, using a short electron bunch traveling along the exit of a waveguide which is at the same time excited by a TM propagating electromagnetic wave. We found that an interesting mode of operation is to drive the waveguide with an excitation frequency very close to the cut off. For such excitation, the corresponding e.m. wave travels with a very large phase velocity which in turn has the effect to increae the wiggling action on the electron bunch. Our method relies also on the coherence of the radiation; that is the bunch length is taken to be considerably shorter than the radiated wavelength. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.44092

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A relativistic field theory of a helix traveling wave tube (TWT) is described for the case in which a thin annular beam propagates through a sheath helix enclosed within a loss‐free wall. The theory is applied to the study of a TWT with an intense relativistic electron beam. The analysis implicitly includes beam space‐charge effects and is valid for arbitrary azimuthal mode number, and the coupled‐wave Pierce theory is recovered in thenear‐resonantlimit. The results indicate that impressive gains and efficiencies are possible in this regime. In addition, the interaction is relatively insensitive to the effects of a beam energy spread.

ISSN:0094-243X    

DOI:10.1063/1.44093

出版商:AIP    

年代:1992

数据来源: AIP