Technical Activities 1983 Center for Basic Standards
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Technical Activities 1983 Center for Basic Standards U S. DEPARTMENT OF COMMERCE National Bureau of Standards National Measurement Laboratory Center for Basic Standards Washington, DC 20234 November 1983 Final Issued January 1984 Prepared for: U S. DEPARTMENT OF COMMERCE National Bureau of Standards Qc /ashington, DC 20234 1 00 -USk p p p I p p V i I » i » i i » i [i fi n NBSIR 83-2793 TECHNICAL ACTIVITIES 1983 CENTER FOR BASIC STANDARDS Karl G. Kessler, Director U.S. DEPARTMENT OF COMMERCE National Bureau of Standards National Measurement Laboratory Center for Basic Standards Washington, DC 20234 November 1 983 Final Issued January 1984 Prepared for: U.S. DEPARTMENT OF COMMERCE National Bureau of Standards Washington, DC 20234 U.S. DEPARTMENT OF COMMERCE, Malcolm Baidrige. Secretary NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director TABLE OF CONTENTS Part II Page Technical Activities: Introduction 1 Quantum Metrology Group 2 Electricity Division 21 Temperature and Pressure Division 81 Length and Mass Division 123 Time and Frequency Division 135 Quantum Physics Division 187 i i I 1 I II II i li 1 1 INTRODUCTION This book is Part II of the 1983 Annual Report of the Center for Basic Standards and contains a summary of the technical activities of the Center for the period October 1, 1982 to September 30, 1983. The Center is one of the five resources and operating units in the National Measurement Laboratory. The summary of activities is organized in six sections, one for the technical activities of the Quantum Metrology Group, and one each for the five divisions of the Center. Each division or group tells its own story in its own way. In general, there is an overview followed by a series of short reports on current projects. Then the publications, invited talks, committee participation and professional interactions during the year are listed. More information about particular work may be desired. To obtain this, the reader should address the individual scientists or their division, c/o Center for Basic Standards, B160 Physics Building, National Bureau of Standards, Washington, D.C. 20234. I M I I fe 1 I QUANTUM METROLOGY GROUP SUMMARY OF ACTIVITIES FISCAL YEAR 1983 I. OVERVIEW In the period of 1979 to 1982 there had been a general contraction of the activities and staff of the Quantum Metrology Group. It is a pleasure to report that this trend was significantly reversed during the past year. Two full-time staff people have been added to the group and three guest workers were in residence. Since no entirely new programs were begun, expansion and acceleration of existing programs in precision x-ray and y-ray wavelength measurements and inner shell physics occurred. In addition the important measurement of a Si crystal lattice spacing was revived. Efforts in the area of precision x-ray and y-ray wavelengths have been concentrated on bringing into operation a four-meter Dumond curved crystal spectrometer. Basil Duval, a guest worker from Culham Laboratory and Oxford University, and Ernie Kessler were the primary contributors to this effort. Firm plans to move a precision double flat crystal spectrometer to the Institut Laue-Langevin (ILL), Grenoble, France, have been made and the instrument should be in place and operational by late November 1983. This activity has been discussed a number of times over the past 4 years but only during the past year have funds and staff made this venture possible. Geoff Greene, a new staff member, will be the resident NBS scientist for the first year of operation. During installation and initial operation, Ernie Kessler and Richard Deslattes will also be at ILL. Precision measurement of high energy gamma-rays (>2 MeV) is the purpose of moving this facility to ILL. A manuscript with Kansas State University and Brookhaven National Laboratory on the Is Lamb shift measurement from C£ + is nearing ^ 7 completion. Data concerning the Is Lamb shift of Ar * recoil ions have been recorded at Gesellschaft fur Schwerionenforschung (GSI) and are being analyzed. Richard Deslattes, Paul Cowan and Robert LaVilla contribute to this effort. The major thrust in the area of inner shell physics has been the preparation of a beamline to be installed at the National Synchrotron Light Source (NSLS). The vacuum envelope has been completely tested, the mirror manipulators are installed, and the monochromator testing is almost complete. Shipment of the beamline to NSLS should occur before the end of 1983. The beamline is primarily the work of Paul Cowan, Terry Jach, A1 Henins, Ernie Kessler and Sean Brennan. The 2 first experiments will use the tunable monochromati zed synchrotron light as a probe of the inner shell region of atomic and molecular species. Brennan, the second new staff person, has had extensive experience at the Stanford Synchrotron Radiation Laboratory (SSRL) before joining the beamline effort during the spring of 1983. His interest in solid state studies using synchrotron radiation is a natural extension of the presently planned studies of atomic and molecular systems. Position sensitive detectors of the backgammon type have been studied by Jochen Barth, a guest worker from the University of Hamburg, and Basil Duval. With the aid of Gabe Luther a number of new detectors were built with some improvements in linearity and resolution. Spectra from chlorine and chlorine molecules were studied by Rupert Perera, a guest worker from Virginia Polytechnic Institute and State University, and Robert LaVilla using a curved crystal spectrometer and position sensitive detector. Information related to mul ti -vacancies and molecular binding is derived from this data. The NBS measurement of the lattice spacing of a Si crystal was published in 1976 and was unchallenged until 1982 when a measurement at PTB differed by 1.8 ppm from the NBS value. After interchange of Si crystal samples, an unexplained difference close to 1.8 ppm still remains. In order to understand this difference the x-ray interferometer facility has been brought back into operation in a manner which will permit a definitive test of the 1976 result and an entirely new measurement if it is necessary. Richard Deslattes is the driving force behind this effort just as he was in 1976 with Geoff Greene, A1 Henins, and Mary Cutkosky making significant contributions. An automated crystal lattice comparison facility is also nearing completion. This facility (primarily the work of A1 Henins) will permit more accurate comparison of NBS and PTB crystal samples as well as more accurate comparison of various crystals in use at NBS. Finally in early August, Richard Deslattes, the group leader, took up residence at the University of Heidelberg as a von Humboldt fellow. In addition to his studies at Heidelberg, he will collaborate on high Z one-electron measurements at GSI and in the high energy y-ray measurements at ILL. Also in August, Jim Snyder moved to NBS Boulder for a year under the auspices of the NBS Gai thersburg-NBS Boulder exchange program. He will be closely associated with John Hall of the Quantum Physics Division. 3 II. TECHNICAL ACTIVITIES 1. Optical Physics J. Snyder Objectives This program is concerned chiefly with experimental laser spectros- copy and the development of related technology. Current Activities The principal investigator (Snyder) is currently a Visiting Fellow at JILA, Boulder, for a period of one year ending September 1984. As a result, some of the activities of this program will be suspended until his return. The collaboration with the West German national standards laboratory (Physikalisch-Technische Bundesanstal t) (PTB) continued this year with a second visit of one month by Snyder to Braunschweig, Germany. The joint experiment is intended to investigate the potential of the narrow calcium intercombination line at 657 nm as a possible future optical frequency standard, as well as to develop the combined spectro- scopic techniques of merged laser-atomic beams and time-domain Ramsey excitation. The dye laser linewidth has been reduced to about 1 kHz during the past year and is expected to be further reduced to the region of a few hundred hertz. The major effort at the present time is to develop efficient high-frequency laser modulators capable of generating the required frequency shift of ^2 GHz. In addition a new collaboration has been initiated with Borde at the University of Paris to model the proposed use of multiple pulse (^40 pulses) Ramsey excitation to reduce fringe complexity and width. The Fizeau wavemeter project is essentially dormant at NBS at the present time. The original instrument continues in full-time routine use in the Temperature and Pressure Measurements and Standards Division (Rosasco). The University of Maryland Fizeau Wavemeter is currently being modified by the introduction of single-mode fiber input coupler. It is hoped that the fiber (which will replace the pinhole used as a spatial filter) will alleviate some problems due to pulsed laser damage of the pinhole substrate. The wire-wrap prototype of the Frequency Meter, although functional, had insufficient noise margin and insufficient speed due to stray capacitance of the wire-wrap pins. A second, printed-circuit prototype was designed using the new NBS computer-aided-design (CAD) facility. This board is currently being built at a commercial firm. Further work on the Mossbauer-drive lambda meter awaits completion of the Frequency Meter electronics. 4 A new collaboration with a group at the University of Rochester was begun to develop interferometers for characterizing the mode structure of pulsed amplified spontaneous emission (ASE) sources. Accomplishments The second round of experiments on calcium at the PTB had limited success due to the limitations of the high-frequency phase modulator. However, the new optical cavity was built and tested successfully, and the modulation and detection electronics were completed.