摘要:

Theoretical and experimental studies conducted by the Stanford Free Electron Laser group have resulted in the first operation of a free‐electron laser amplifier and free‐electron laser oscillator. Two superconducting helically wound periodic magnetics have been constructed for use with the laser. In this paper we present a discussion of design considerations and test results for the two magnets. The tests included measurement of the magnitude and the variation of the transverse magnetic field with radius in the bore of the magnets, the critical current, and the intensity, angular distribution, and spectrum of the spontaneous radiation emitted by electrons moving through the field.

ISSN:0034-6748    

DOI:10.1063/1.1135721

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The operation of a pulsed, watt‐level, low‐pressure far infrared (FIR) laser is described. Single mode output powers of 0.1–1 W are obtained from several molecular gases in the 300–1200 &mgr;m region. Plasma diagnostic applications are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1135722

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A 16‐bit microcomputer has been coupled to an optical multichannel analyser (OMA). This paper describes the hardware interface which has been developed so as to permit the transfer of spectra in both directions, from the OMA into the RAM extension memory of the microprocessing system, and back from there into either one memory of the OMA. A few elementary circuit modifications of the OMA itself are required to allow that back transfer, and are also described. A brief outline of the software is given. The adjunction of the microcomputer to the OMA makes it possible to operate this instrument in a new mode: real time with optical integration and nevertheless without any baseline.

ISSN:0034-6748    

DOI:10.1063/1.1135723

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new and improved method for continuous frequency calibration of the super‐regenerative oscillator spectrum is described. The arrangement employs a Hewlett–Packard Model HP5345A reciprocal frequency counter capable of measuring the carrier frequency of rf pulses. The counter gate time is externally controlled via the quench pulses. High‐resolution measurements are obtained through the use of the frequency‐averaging mode provided by the counter. Three successive digits are displayed on a two‐channel recorder using a digital‐to‐analog converter along with the lock‐in output. This method provides automatic and continous high‐accuracy frequency calibration of the spectrum which is independent of the rf level, quench frequency, and FM amplitude.

ISSN:0034-6748    

DOI:10.1063/1.1135724

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The performance of a cubical permanent magnet generated line‐cusp ion source has been investigated for use with neutral beam injectors. This source has been operated with discharge currents greater than 500 A and ion current densities higher than 400 mA/cm2at the extraction grid. The uniformity of the density profile across the extraction area is found to be dependent on the gas pressure. By using a fast Langmuir probe sweeping circuit, the electron temperature and the plasma density and potential have been analyzed for different discharge powers and gas pressures. The heat load on the plasma grid when it is electrically floating or connected to the negative cathode has been compared calorimetrically. The use of lanthanum hexaboride and impregnated oxide cathodes have been investigated for the purpose of long pulse operation. The phenomenon of mode flipping is found to occur quite frequently during a discharge with these magnetic‐field‐free cathodes. Species composition as a function of discharge power and chamber length is measured by a mass spectrometer.

ISSN:0034-6748    

DOI:10.1063/1.1135725

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An experimental facility for the realization of plane Couette flow is described. In this, the moving wall is a rigid plate propelled through air by the carriage of a towing channel, and the fixed wall is a stationary bench constructed alongside the towing tank. This particular arrangement makes it possible to introduce the important parameter of wall roughness into experimental investigations of this flow.

ISSN:0034-6748    

DOI:10.1063/1.1135726

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The conversion of a Cary 60 spectropolarimeter to a fast circular dichroism instrument (CD) using CD detection for standard rapid reaction techniques and for recording normal CD spectra is described. Although the optical setup remains nearly the same, the electronics are modified to increase the frequency response. The use of a 18‐kHz piezo‐optical birefringence modulator allows measurements of relaxation times down to 5 ms. As an example of the kind of data obtainable with this instrument, measurements are presented on the acid denaturation of hemoglobin in the time range of 100 ms.

ISSN:0034-6748    

DOI:10.1063/1.1135727

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A cell design is presented for experiments with hydrostatic pressures up to 25 kbar. The pressure‐transmitting medium around the sample is candle wax, which is sealed in the cavity with molybdenum disulfide impregnated nylon and aluminum disks. This approach showed no detectable leakage to 25 kbar. Internal cavity pressure is computed from measurements of the applied load on the top piston, the transmitted load to the lower piston, and the frictional forces transmitted by the seals into the pressure vessel and the cell body. Internal pressure thus measured and phase‐transition pressure data from RbCl and KBr are all within 9% of each other for the pressure range 3–25 kbar.

ISSN:0034-6748    

DOI:10.1063/1.1135716

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We describe a lumped‐component stabilized point contact SQUID magnetometer, biased at 430 MHz and utilizing a cooled (4.2 K) GaAs FET preamplifier. The system incorporateds a full‐bandwidth (5–10 MHz) flux‐locked loop and has an overall flux sensitivity of 1×10−5&Fgr;0/(Hz)1/2, corresponding to an energy sensitivity ≃4.5×10−31J/Hz.

ISSN:0034-6748    

DOI:10.1063/1.1135717

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A simple precooling system for a superconducting magnet is developed using a Cryomech GB02 cryocooler and gas filled thermal switches. A superconducting magnet (NbTi wire, 7 T of maximum field, 5.6 kg of weight) is precooled to 16 K in about 70 h without any manual control. Heat transfer rate of each thermal switch (H2or N2gas filled at 1.3 MPa at room temperature) is about 3×10−1W/K during the ON state, and 5×10−3W/K during the OFF state.

ISSN:0034-6748    

DOI:10.1063/1.1135718

出版商:AIP    

年代:1979

数据来源: AIP