Contains research objectives and reports on two research projects.Lincoln Laboratory, Purchase Order DDL-B222Department of the ArmyDeparment of the NavyDepartment of the Air Force under Contract AF19(122)-45

Brown, H. H., Jr.

King, J. G.

Vessot, R. F. C.

Zacharias, J. R.

DSpace@MIT

X. ATOMIC BEAMSProf. J. R. Zacharias Prof. C. L. Searle G. W. StrokeProf. J. G. King Dr. R. F. C. Vessot R. WeissH. H. Brown, Jr.RESEARCH OBJECTIVESThe distributions of electric charge and magnetism in an atomic nucleus are usuallydescribed in terms of multipole moments limited in number by the magnitude of thenuclear angular momentum. In this laboratory, atomic-beam techniques are used todetermine such electric and magnetic moments. In addition, information about theradial distribution of nuclear magnetism can be obtained in cases in which more thanone isotope is available. These techniques lend themselves to such precision that theywere used in this laboratory for the development of the most accurate atomic clock.In turn, these clocks are being used to make studies on the nature of time itself. Pre-cision apparatus is under construction to observe not only the dependence of atomictime on gravitational potential but also the epochal dependence of nuclear, gravitational,and atomic time. Similar studies are being made on the velocity of light.J. G. King, J. R. ZachariasA. HYPERFINE STRUCTURE OF BROMINESince the Quarterly Progress Report of January 15, 1958 (p. 56), three of the sixrequired klystrons have been phase-locked to a crystal standard. Great difficulty wasexperienced in obtaining the required vacuum in the vacuum envelope. Recently, someliquid-air traps and a diffusion pump were added to the apparatus, and we have suc-ceeded in reaching the required pressure, although it is doubtful whether the extra trapsand pump helped.A bromine beam has been observed, but it was not of the required shape. Datataken indicate that the source may be too broad. This broadening might be the resultof scattering in the oven chamber. Another possibility is that the bromine sits down onthe oven chamber aperture, and then is re-emitted. A liquid-air baffle cooked in theoven chamber is being considered.H. H. Brown, Jr., J. G. KingB. CESIUM MASERThe apparatus has been completed and measurements of beam intensities made9 10with the use of a hot wave detector indicate that from 10 to 10 particles per secondare available in the desired state.This research was supported in part by Purchase Order DDL-B222 with LincolnLaboratory, which is supported by the Department of the Army, the Department of theNavy, and the Department of the Air Force under Contract AF19(122)-458 with M.I.T.(X. ATOMIC BEAMS)Measurements of the vacuum-system pumping speed show that a pressure in thehelium cavity of 10-2 mm Hg at 40 K results in a pressure of 5 X 10 - 6 mm g in theupper can. The lower system can be held to a pressure of better than 5 X 10-8 whilethese conditions are maintained.Runs in which liquid helium was used for cavity cooling were made in an effort tofind the cesium signal. Cavity pressure was varied from 10 - 2 to 10 - 4 mm Hg andstimulator power was varied 40 db. No signal has been obtained thus far. Recentmeasurements of receiver noise figure show that a vast improvement is necessary, andwork will continue in this direction.R. F. C. Vessot

Atomic Beams

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Atomic Beams

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