H. L. Anderson

On the detection of 50 MeV γ-rays with a large modularized NaI(Tl) detector☆

Abstract An array of 45 NaI(Tl) crystals modules, each in 20 in. in length and hexagonal in cross section with six 3 in. sides, has been operated as a detector of 50 MeV γ-rays in a search for the decay μ + →e + γ . The calibration procedure used for this detector and the resolutions achieved in γ-ray energy, time of detection and point of impact on the detector face are described.

Alpha particle thickness gauge using a solid state detector

An alpha particle thickness gage is described in wbich the shift in energy of alpha -particles in passing through the material is observed directly by means of a solid state detector and pulse height analyzer. Measurements of the thickness of 1 mg/cm/sup 2/ foils can be made easily to better than 1%. The arrangement is useful for absolute energy loss measurements and some results are given for mylar. (auth)

Double Magnetic Lens Nuclear Spectrometer

A large double magnetic lens spectrometer has been constructed for the study of gamma‐ and beta‐ray spectra. The magnetic field is produced by two identical coaxial water‐cooled coils, each 10.2 cm wide, 31.7 cm I.D., 73.7 cm O.D., and spaced 95.6 cm apart. The source is placed on the axis at the center of one coil and the detector is placed on the axis at the center of the other. The instrument is characterized by a large transmission with moderate resolution. Scattering is virtually absent because of the nature of the trajectories which are used, and because the large dimensions have made possible the removal of scattering material to a considerable distance from the source. The design has lent itself easily to the application of accelerating voltages at the detector admitting the detection of beta‐rays down to 1 kilovolt. The maximum energy conveniently studied with the present arrangement is 2.8 Mev. Beryllium‐coated Zapon films of thickness 0.01 mg/cm2 have been used to mount sources. Charge does not accumulate on these sources. Observations with a Cs137 source 4 mm in diameter have shown a transmission of 1.4 percent with a resolution of 1 percent. The appearance of the internal conversion and Auger electron lines testifies to the absence of appreciable scattering.

Synchrocyclotron for 450‐Mev Protons

A 170‐inch synchrocyclotron recently completed at the Institute for Nuclear Studies, The University of Chicago, is described. It is capable of accelerating protons to an energy of 450 Mev, deuterons to an energy of 256 Mev, and alpha‐particles to an energy of 512 Mev. The magnet poles are especially contoured to give a field of 18,600 gauss in the center decreasing to 17,600 gauss at radius 76 inches. The radiofrequency is modulated by means of a rotating condenser in a three‐quarter wave resonant line oscillator. A circulating beam of about one microampere of 450‐Mev protons is normally obtained. This beam falling on an internal beryllium target produces about 4×1010 π‐mesons per second. Some of these π‐mesons emerge from the cyclotron, pass through channels in a heavy shield and are available in well‐collimated beams, well‐defined in energy. The present beams range in energy from 66 Mev to 230 Mev for π− mesons and from 66 to 145 Mev for π+ mesons. In the external 122‐Mev π− beam there are 1000π− mesons...

Regulator Systems for Electromagnets

A regulator for maintaining constant, to better than 0.1 percent over long periods, the magnetic field of large (100 kw) electromagnets is described. This consists of two basic components: (1) A vacuum tube voltage regulator which compensates for rapid changes in voltage and thus anticipates the change in current which would result. (2) A current actuated element arranged so as to alter the operating point of the voltage regulator in order to compensate for slow changes in current due to changes in the temperature of the windings. Very rapid regulator action is secured with no drift or hunting to the limit specified.

A multiwire proportional chamber based system for digitizing electrophoretic gels

Abstract A system for studying proteins which utilizes a multiwire proportional chamber is described. Essential elements of this system are a strong magnetic field and a high speed bit-slice prepocessor based data acquisition system.

Fiber-optics light guides for thin scintillators☆

Abstract The use of plastic fiber-optic bundles as flexible light guides for thin scintillators is described. In a test as a transmission counter for surface muons (30 MeV/ c ) an efficiency >99% was obtained. It operated with a positron efficiency

Spark Chamber Data‐Handling System Using Television Cameras

A spark chamber data recording system directly compatible with an IBM 7094 computer is described. The basic information‐gathering elements are two closed‐circuit television cameras scanning parallel to the spark chamber plates. The spark coordinates are digitized and recorded on digital magnetic tape. Basic considerations, operation, and results of linearity and cosmic ray tests are given.

Determination of isotopic differences in mesic x-rays in calcium

Measurements of the isotopic shift in the energies of the 2p- 1s transitions in targets of Ca/sup 44/ and Ca/sup 60/ were made to obtain information about the distribution of charges in the nucleus. It was found that this transition in the mu -mesic atom of Ca/sup 44/ is 4.8 plus or minus 2.0 kev more energetic than the corresponding transition in the mu -mesic atom of Ca/ sup 40/. (R.E.U.)

The Preparation of Pressed Ra+Be Neutron Sources

A method for preparing pressed Ra+Be fast neutron sources is described in detail. Such sources can be made to contain as much as 5 g of Ra. They have the advantage of small volume and constancy of neutron output. The yield of fast neutrons per sec. per g of Ra can be obtained from the relationship yield=1.7×107MBeMBe+MRaBr2.