Advances in Cryogenic Engineering – serie

The ninth International Cryogenic Materials Conference (ICMC) was held on the campus of the University of Alabama at Huntsville (UAH) in collaboration with the Cryogenic Engineering Conference (CEC) on June 11-14, 1991. The continuing bond between these two major conferences in the field of cryogenics is indicative of the extreme interdependence of their subject matter. The major purpose of the conference is sharing of the latest advances in low temperature materials science and technology. However, the many side benefits which accrue when this many experts gather, such as identification of new research areas, formation of new collaborations which often cross the boundaries of both scientific discipline and politics, and a chance for those new to the field to meet the old-timers, may override the stated purpose. This 1991 ICMC was chaired by F. R. Fickett of the National Institute of Standards and Technology. K. T. Hartwig, of Texas A&M served as Program Chairman with the assistance of eleven other Program Committee members. We especially appreciate the contributions of the CEC board and its Conference Chairman, J. Hendricks of Alabama Cryogenic Engineering, to the organization. of this joint conference. UAH hosted the conference. The local arrangements and management, under the watchful eye of Ann Yelle and Mary Beth Magathan of the UAH conference staff, were excellent. Participation in the CEC/ICMC continues to exceed expectations with 650 registrants for the combined conference.

The 1993 International Cryogenic Materials Conference (ICMC) was held at the Albuquer- que Convention Center in Albuquerque, New Mexico in conjunction with the Cryogenic Engi- neering Conference (CEC) on July 12-16. The interdependent subjects of the two conferences attracted more than eight hundred participants, who came to share the tatest advances in low- temperature materials science and technology. They also came for the important byproducts of the conferences: identification of new research areas, exploration of collaborative research possi- bilities, and the establishment and renewal of professional relationships. K. Theodore Hartwig (Texas A&M University), asChairman ofthe 1993 ICMC; T. Scott Kreilick (Hudson International Conductors), as Program Chairman; and thirteen other Program Committee members expertly arranged the ICMC sessions and activities. The contributions of the CEC board and its Conference Chairman Walter F. Stewart of the Los Alamos National Laboratory (LANL) were centrat to the organization ofthe tenth CEC/ICMC, which was hosted by LANL. The local arrangements and management, under the skillful guidance of Jan C. Hull (LANL), were exemplary.Frederick Edeskuty (LANL) served as Exhibits Chairman, and L. Kim Nguyen (LANL), as Conference Support Liaison.

The Albuquerque Convention Center was the venue for the 1993 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. Walter F. Stewart, of Los Alamos National Laboratory, was conference chairman. Albuquerque is near Los Alamos National Laboratory which has been a significant contributor to the cryogenics community since the early days of the Manhattan Project. Albuquerque is also the home of the Air Force's Phillips Laboratory which has a lead role in developing cryocoolers. The program consisted of 322 CEC papers, more than a 30% increase from CEC-91 and 20% more than CEC-89. This was the largest number of papers ever submitted to the CEC. Of these, 249 papers are published here, in Volume 39 of Advances in Cryogenic Engineering. Once again the volume is published in two books. This volume includes a cumulative index for the CEC volumes from 1975-1993 (volumes 21,23,25,27,29,31,33,35,37, and 39 of Advances in Cryogenic Engineering). The first 20 volumes are indexed in Volume 20. A companion cumulative index for the ICMC volumes (volumes 22 through 40) appears in Volume 40. This is my first volume as editor. I would not have been able to have done it without the assistance of the many reviewers. Especially appreciated was the instruction manual left me by the previous editor, Ron Fast.

The Hyatt Regency Hotel, Columbus, Ohio was the venue for the 1995 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. Jim Peeples, of CVI, Inc., was conference chairman. Columbus is the home of the Battelle Memorial Institute, a pioneer in cryogenic materials development; the home of CVI, Inc., and Lake Shore Cryotronics, Inc., two leading manufacturers of cryogenic equipment; and it is the home of Ohio State University, where research on liquid helium has long been conducted. The program consisted of 315 CEC papers, nearly the same number as for CEC-91. This was the second largest number of papers ever submitted to the CEC. Of these, 252 papers are published here, in Volume 41 of Advances in Cryogenic Engineering. Once again the volume is published in two books. This volume includes a number of photographs taken during the awards lunch on July 20, 1995. Photographs have often been taken during the conferences, but they have never been used. The pictures are of the awardees, the conference chairs, and the organizers. They are distributed through out the books on pages that would otherwise have been blank. The pictures can be found on the following pages: 28, 232, 334, 536, 640, 826, 990, 1032, 1202, 1462,1682,1888, and 1994.

The 1995 International Cryogenic Materials Conference (lCMC) was held at the Greater Columbus Convention Center in Columbus, Ohio, in conjunction with the Cryogenic Engineering Conference (CEC) on July 17-21. The interdependent subjects of the two conferences attracted more than eight hundred participants, who came to share the latest advances in low-temperature materials science and technology. They also came for the important by products of the conferences: identification of new research areas, of collaborative research possibilities, and the establishment and renewal of exploration professional relationships. Ted Collings (Ohio State University), as Chairmen of the 1995 ICMC; Ted Hartwig (Texas A&M University), as Program Chairman; and twenty-one other Program Committee members expertly arranged the ICMC technical sessions and related activities. The contributions of the CEC board and its Conference Chairman James B. Peeples of CVI, Inc., were central to the success of the eleventh CEC/ICMC. Jeff Bergen of Lake Shore Cryogenics served as Exhibits Chairman. Local arrangements and conference management were expertly handled under the guidance of Centennial Conferences, Inc. Skillful assistance with editing and preparation ofthese proceedings was provided by Ms. Vicky Bardos ofSynchrony, Inc.

The Oregon Convention Center, Portland, Oregon, was the venue for the 1997 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. John Barclay, of the University of Victoria, and David Smathers, of Cabot Performance Materials, were conference chairmen. Portland is the home of Northwest Natural Gas, a pioneer in the use of liquid natural gas, and Portland State University, where cryogenic research has long been conducted. The program consisted of 350 CEC papers, considerable more than CEC-95. This was the largest number of papers ever submitted to the CEC. Of these, 263 papers are published here, in Volume 43 of Advances in Cryogenic Engineering. Once again the volume is published in two books. CEC PAPER REVIEW PROCESS Since 1954 Advances in Cryogenic Engineering has been the archival publication of papers presented at the biennial CEC!ICMC conferences. The publication includes invited, unsolicited, and government sponsored research papers in the research areas of cryogenic engineering and applications. All of the papers published must (1) be presented at the conference, (2) pass the peer review process, and (3) report previously unpublished theoretical studies, reviews, or advances in cryogenic engineering.

Since 1954 Advances in Cryogenic Engineering has been the archival publication of papers presented at the biennial CEC/ICMC conferences. Advances in Cryogenic Engineering resides throughout the world in the libraries of most institutions that conduct research and development in cryogenic engineering and applied superconductivity. The publication includes invited, unsolicited, and government-sponsored research papers in the research areas of superconductors and structural materials for cryogenic applications. All of the papers published must (1) be presented at the conference, (2) pass the review process, and (3) report previously unpublished theoretical studies, reviews, or measurements of material properties at low temperatures.

There is an increasing effort, world wide, to advance the uses of superconductivity in power engineering and utility applications. Many of the technical papers here, on materials, applications and economics, reflect this tendency. There is also extensive coverage of both low and high temperature superconductivity and cryogenic materials and testing.

The 1989 Cryogenic Engineering Conference, meeting jointly with the International Cryogenic Materials Conference, was held on the campus of the University of California, Los Angeles from July 24 to 28. Professor T.H.K. Frederking was the conference chairman. The Conference had previously met at U.C.L.A. in 1962 and 1969. A special symposium, "A Half Century of Superfluid Helium," was a significant part of the program of CEC-89. We were especially fortunate to have Professor Jack Allen of the University of St. Andrews, Scotland present at the Conference; his paper, "Early Superfluidity in Cambridge, 1936 to 1939," was a delightful, often humorous account of the early experimental work with superfluid helium. Professors V.L. Ginzburg and J.L. Olesen could not be present for the Symposium, but provided papers which are published in these proceedings. The late Bill Fairbank, responding graciously to a last-minute invitation from Professor Frederking, presented a wonderful account of superfluid research in the United States in the post-war years.

The Fourth International Cryogenic Materials Conference (ICMC) was held in San Diego, California in conjunction with the Cryogenic Engineer­ ing Conference (CEC) on August 10-l4, 1981. The synergism produced by conducting the two conferences together remains very strong. In the ap­ pl1cation of cryogenic technology, materials continue to be a demanding challenge, and sometimes, an obstacle. The association of materials and cryogenic engineers increases their awareness of recent research in each other's fields and influences the course of future research. Many contributed to the success of the 1981 conference. J. W. Morris of the University of California--Berkeley was ICMC Conference Chairman. E. N. C. Dalder of Lawrence Livermore Laboratories was ICMC Structural Program Chairman; D. C. Larbalestier of the University of Wisconsin-­ Madison, and D. K. Finnemore of Iowa State University were Superconducting Materials Program Chairmen. Local arrangments were expertly coordinated by R. E. Tatro of General Dynamics--San Diego. The CEC Board, especia11y their conference chairman, T. M. Flynn, of the National Bureau of Stan­ dards, Boulder, contributed very substantia1ly to conference planning and implementation. All of their efforts provided the foundation of the largest CEC/ICMC ever. We thank the Office of Naval Research and the Office of Fusion Energy and Basic Energy Sciences of the Department of Energy for providing needed financial support for the conference. Fina11y, we especially thank M. Stieg, who prepared the papers for the new procedures and format used in this volume.

In late 1877, Louis Cailletete in France and Raoul Pictet in Switzerland independently succeeded in liquefying oxygen, thereby proving a hypothesis set forth by Antoine Lavoisier nearly 100 years earlier. The theme of the 1977 Cryogenic Engineering Conference "Cryogenics: A Century of Progress-A Chal­ lenge for the Future" properly commemorated this accomplishment by reviewing some of the noteworthy advances since that time and outlining many advances still to come. Both Volumes 23 and 24 of this series provide a good account of the many contributions that were presented at this conference. The 1977 Cryogenic Engineering Conference was appropriately again held in Boulder, Colorado where the first Cryogenic Engineering Conference was initiated 23 years ago by the late Russell B. Scott, then Chief of the Cryogenic Engineering Laboratory of the National Bureau of Standards. The Cryogenic Engineering Conference Board is extremely grateful to members of the National Bureau of Standards and the University of Colorado for serving as hosts for this meeting of cryogenic specialists from all over the world. The Cryogenic Engineering Conference is again pleased to have had the International Cryogenic Materials Conference co-host this biennial meeting for the second time in succession. This joint effort again has permitted an in-depth coverage of research on technical materials in areas currently receiving primary attention by the cryogenic engineering community. The Proceedings of the Inter­ national Cryogenic Materials Conference will be published as Volume 24 of the Advances in Cryogenic Engineering.

The Albuquerque Convention Center was the venue for the 1993 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. Walter F. Stewart, of Los Alamos National Laboratory, was conference chairman. Albuquerque is near Los Alamos National Laboratory which has been a significant contributor to the cryogenics community since the early days of the Manhattan Project. Albuquerque is also the home of the Air Force's Phillips Laboratory which has a lead role in developing cryocoolers. The program consisted of 322 CEC papers, more than a 30% increase from CEC-91 and 20% more than CEC-89. This was the largest number of papers ever submitted to the CEC. Of these, 249 papers are published here, in Volume 39 of Advances in Cryogenic Engineering. Once again the volume is published in two books. This volume includes a cumulative index for the CEC volumes from 1975-1993 (volumes 21,23,25,27,29,31,33,35,37, and 39 of Advances in Cryogenic Engineering). The first 20 volumes are indexed in Volume 20. A companion cumulative index for the ICMC volumes (volumes 22 through 40) appears in Volume 40. This is my first volume as editor. I would not have been able to have done it without the assistance of the many reviewers. Especially appreciated was the instruction manual left me by the previous editor, Ron Fast.

Proceedings of the 1991 Cryogenic Engineering Conference held in Huntsville, Alabama, June 11-14, 1991.

In recent years, the technology of cryogenic comminution has been widely applied in the field of chemical engineering, food making, medicine production, and particularly in recycling of waste materials. Because of the increasing pollution of waste tires and the shortage of raw rubber resource, the recycling process for waste rubber products has become important and commercially viable. This technology has shown a great number of advantages such as causing no environmental pollution, requiring low energy consumption and producing high quality products. Hence, the normal crusher which was used to reclaim materials, such as waste tires, nylon, plastic and many polymer materials at atmospheric 12 temperature is being replaced by a cryogenic crusher. • In the cryogenic crusher, the property of the milled material is usually very sensitive to temperature change. When a crusher is in operation, it will generate a great deal of heat that causes the material temperature increased. Once the temperature increases over the vitrification temperature, the material property will change and lose the brittle behavior causing the energy consumption to rise sharply. Consequently, the comminution process cannot be continued. Therefore, it is believed that the cryogenic crusher is the most critical component in the cryogenic comminution system. The research on the temperature increase and energy consumption in the cryogenic crusher is not only to reduce the energy consumption of the crasher, but also to reduce the energy consumption of the cryogenic system.

The Hyatt Regency Hotel, Columbus, Ohio was the venue for the 1995 Cryogenic Engineering Conference. The meeting was held jointly with the International Cryogenic Materials Conference. Jim Peeples, of CVI, Inc., was conference chairman. Columbus is the home of the Battelle Memorial Institute, a pioneer in cryogenic materials development; the home of CVI, Inc., and Lake Shore Cryotronics, Inc., two leading manufacturers of cryogenic equipment; and it is the home of Ohio State University, where research on liquid helium has long been conducted. The program consisted of 315 CEC papers, nearly the same number as for CEC-91. This was the second largest number of papers ever submitted to the CEC. Of these, 252 papers are published here, in Volume 41 of Advances in Cryogenic Engineering. Once again the volume is published in two books. This volume includes a number of photographs taken during the awards lunch on July 20, 1995. Photographs have often been taken during the conferences, but they have never been used. The pictures are of the awardees, the conference chairs, and the organizers. They are distributed through out the books on pages that would otherwise have been blank. The pictures can be found on the following pages: 28, 232, 334, 536, 640, 826, 990, 1032, 1202, 1462,1682,1888, and 1994.

The year 1973 marked the first time that Atlanta, one of the cultural centers of the South, has hosted the Cryogenic Engineering Conference since its beginning in 1954. The Cryogenic Engineering Conference gratefully acknowledges the hospital­ ity of the Georgia Institute of Technology and the assistance of W. T. Ziegler and his staff in making the visit to Atlanta a pleasant and memorable one. Several significant changes were initiated at the 1973 Cryogenic Engineering Conference. These included a Conference theme on the subject of "Energy and the Environment," a new Conference format, and the beginning of a new Conference frequency of biennial meetings. While retaining the traditional topics of previous meetings, the 1973 Cryogenic Engineering Conference focused on the role of cryo­ genic engineering in the generation, distribution, and conversion of energy, and the related environmental effects. In these areas, much of the current interest stems from the environmental effects of LNG and liquid hydrogen as compared with other competing energy forms. These rapidly expanding areas may provide the impetus to cryogenic engineering in the 1970's that the space program provided in the 1960's. The Conference format was altered by the use of numerous invited papers highlighting the theme. These presentations were concentrated in plenary sessions initiating each day's activities, and in seminars designed to summarize the various aspects of the theme.

The First International Cryogenic Materials Conference (ICMC) provided a new forum for the presentation of low-temperature materials research. The confer­ ence, held in conjunction with the 1975 Cryogenic Engineering Conference, provided materials research personnel with excellent exposure to current develop­ ments in the cryogenics field and beneficial interactions with designers of cryogenic systems. Because of the large response to a late call for papers, the enthusiasm and encouragement at the meeting, and the wide spectrum and high quality of papers, the Second International Cryogenic Materials Conference is being planned along with the 1977 Cryogenic Engineering Conference for Boulder, Colorado, in the summer of 1977. The success of the First International Cryogenic Materials Conference was certainly in large measure due to the excellent hospitality of our Canadian hosts, the Royal Military College of Canada and Queen's University in Kingston, Ontario. In particular, the efforts of A. C. Leonard and his staff ensured an excellent conference and a pleasant and memorable visit to Canada. The Cryogenic Engineering Conference Board was both generous and skillful in helping to initiate this new conference and their guidance and acceptance is gratefully acknowledged. The Cryogenic Engineering Conference program chairman, M. J. Hiza, greatly facilitated the interaction for the two conferences and provided valuable assistance in generat­ ing a workable program. The proceedings of the 1975 Cryogenic Engineering Conference are published as Volume 21 of the Advances in Cryogenic Engineering and include many papers indicating innovative use of new cryogenic materials properties data.

The Second International Cryogenic Materials Conference (ICMC) was held in Boulder, Colorado, in conjunction with the 1977 Cryogenic Engineering Con­ ference (CEC). Special thanks must be given to the University of Colorado for their skillful hosting of these two conferences. Collaboration between the two con­ ferences has been mutually beneficial, providing the materials special ist with insight into new applications and design concepts and the cryogenic engineer with exposure to modern materials accomplishments and potentials. The Proceedings of the 1977 Cryogenic Engineering Conference are published in Volume 23 of Advances in Cryogenic Engineering. Both conferences will be held again simul­ taneously in Madison, Wisconsin, in August 1979. The success and growth of the two International Cryogenic Materials Con­ ferences have led to the formation of an ICMC Board of Directors. The board members will serve a four-year term and include: Chairman, R. P. Reed (U.S.), R. W. Boom (U.S.), A. F. Clark (U.S.), G. Hartwig (W. Germany), J. W. Morris (U.S.), M. Suenaga (U.S.), K. Tachikawa (Japan), J. Tanaka (Japan), and K. A. Yushchenko (USSR).

The Cryogenic Engineering Conference celebrated its Silver Anniversary at the 1979 Conference held at Madison, Wisconsin. For many it provided an opportunity to reminisce about the first Cryogenic Engineering Conference convened at the National Bureau of Standards in Boulder, Colorado and also about the many following conferences and advances that had been reported at these conferences. It is difficult to realize that the first Cryogenic Engineering Conference was held before the advent of multilayer insulation, the space age, large-scale LNG Operations and superconductivity applications. The evolution of these activities has been carefully recorded in past volumes of the Advances in Cryogenic Engineering. · Once again, the Cryogenic Engineering Conference is happy to have had the International Cryogenic Materials Conference cohost this meeting at the University of Wisconsin. Collaboration between these two conferences has proven to be mutually beneficial by providing the cryogenic engineer with an in-depth exposure to materials properties, selection, and utilization to complement the exposure to new applications and design concepts. The papers presented at this joint conference as part of the International Cryogenic Materials Conference will be published as Volume 26 of the Advances in Cryogenic Engineering.

The Fifth International Cryogenic Materials Conference (ICMC) was held in Colorado Springs, Colorado in collaboration with the Cryogenic Engineering Conference (CEC) on August 15-19, 1983. The growth and success of the joint conferences is a result of their complementary program and close cooperation. Materials remain a challenge in the application of cryogenic technology and sometimes, as in the case of superconductors, are the driving force for the technology. The association of materials and cryogenic engineers increases their awareness of recent research in their respective fi. elds and influences the course of future research and applications. Many contributed to the success of the 1983 conference: E. W. Collings of Battelle Memorial Institute was the ICMC Confer­ ence Chairman; M. Suenaga of Brookhaven National Laboratories, the ICMC Program Chairman; and L. L. Sparks of the National Bureau of Standards, the ICMC Local Arrangements Chairman. J. M. Wells and A. I. Braginski of Westinghouse R & D Center, G. Hartwig of the Nuclear Research Center of Karlsruhe, and K. T. Hartwig of the University of Wisconsin assisted the Program Chairman in metallic metals, superconducting materials, nonmetallic materials, and cryo­ physical properties, respectively. Excellent conference management was provided by Centennial Conferences. We especially thank M. Stieg, who coordinated the preparation of the papers for this volume. The CEC Board, especially their conference chairman, C. D. Henning of Lawrence Livermore National Laboratories, contributed very substan­ tially to conference planning and implementation.

The Sixth International Cryogenic Materials Conference (ICMC) was held on the campus of Massachusetts Institute of Technology in Cambridge in col­ laboration with the Cryogenic Engineering Conference (CEC) on August 12-16, 1985. The complementary program and the interdependence of these two dis­ ciplines foster the conference. Its manifest purpose is sharing the latest advances in low temperature materials science and technology. Equally im­ portant, areas of needed research are identified, prioriti-es for new research are set, and an increased appreciation of interdisciplinary, interlaboratory, and international cooperation ensues. The success of the conference is the result of the. able leadership and hard work of many people: S. Foner of M.I.T. coordinated ICMC efforts as its Conference Chairman. A. I. Braginski of Westinghouse R&D Center planned the program with the assistance of Cochairmen E. N. C. Dalder of Lawrence Livermore National Laboratory, T. P. Orlando of M.I.T., D. O. Welch of Brookhaven National Laboratory, and numerous other committee members. A. M. Dawson of M.I.T., Chairman of Local Arrangements, and G. M. Fitzgerald, Chairman of Special Events, skillfully managed the joint conference. The contributions of the CEC Board, and particularly its conference chairman, J. L. Smith, Jr. of M.I.T., to the organization of the joint conference are also gratefully acknm.ledged.

The 1987 joint Cryogenic Engineering Conference/International Cryogenic Materials Conference was held at the Pheasant Run Resort, St. Charles, lliinois from June 14 to 18. Fermi National Accelerator Laboratory, located a few kilometers from Pheasant Run, was the host for this conference. There is a great deal of cryogenic research and development underway at Fermilab and many applications of cryogenic materials and systems are in rou­ tine, daily use at the Tevatron. The technical program for the joint conference had over 300 invited and contributed papers from many different countries. The CEC board and I have tried to dramatically shorten the publication time of this volume of Advances in Cryogenic Engineering. In order to help meet the goal of the February publication, I asked the reviewers to complete their reviews before leaving Pheasant Run, after the conference. I would like to thank all of the reviewers for their prompt and throughtful reviews. I very much appreciate the authors following the prescribed format and responding quickly to my requests for revisions.

The editors are pleased to present to the nuclear com­ munity our new-look annual review. In its new look, with Plenum our new publisher, we may hope for a more rapid pre­ sentation to our audience of the contents for their consi­ deration; the contents themselves, however, are motivated from the same spirit as the first nine volumes, reviews of important developments in both a historical and an anticipa­ tory vein, interspersed with occasional new contributions that seem to the editors to have more than ephemeral interest. In this volume the articles are representative of the editorial board policy of covering a range of pertinent topics from abstract theory to practice and include reviews of both sorts with a spicing of something new. Conn's review of a conceptual design of a fusion reactor is timely in bringing to the attention of the general nuclear community what is perhaps well known to those working in fusion - that practical fusion reactors are going to require much skillful and complex engineering to make the bright hopes of fusion as the inex­ haustible energy source bear fruit. Werner's review of nu­ merical solutions for fission reactor kinetics, while not exactly backward looking, is at least directed to what is now a well established, almost conventional field. Fabic's sum­ mary of the current loss-of-coolant accident codes is one realisation of the intensity of effort that enables us to call a light water reactor 'conventional.

Cryogenic engineering is concerned with developing and improving low temperature processes, techniques, and equipment; It is rather difficult to assign a definite temperature which serves to divide refrigerating engineering from cryogenic engineering.

These sessions were divided into the following general topics: Cryogenic Processes Cryogenic Equipment Cryogenic Properties Cryogenic Applications Bubble Chambers The division in some cases had to be somewhat arbitrary since several papers could have been classified under more than one general topic.

Allison Division, General Motor s American Messer Corporation Aro Equipment Corporation Beech Aircraft Corporation Bell Aircraft Boeing Airplane Company Cambridge Corporation Convair Curtiss-Wright Corporation Garrett Corporation General Electric Company Herrick L.

Support from the National Science Foundation has made it possible for the tenth annual Cryogenic Engineering Conference, hosted by the University of Pennsylvania and capably directed by K. R. Atkins and his staff, to emphasize the major international advances in cryogenic engineering. This specific emphasis resulted in a final program of over one hundred papers and has made it necessary to publish the proceedings of the conference in two volumes. The first volume will be similar in nature to previous volumes in this series, while the second volume will feature the international aspect of the conference program. The latter volume, because of this distinction, will be entitled International Advances in Cryogenic Engineering. As in the past, the Cryogenic Engineering Conference Committee gratefully acknow­ ledges the assistance of all the dedicated workers in the cryogenic field who have contributed their time in reviewing the preliminary papers for the program and the final manuscripts for this volume. Since the list of participants in this thankless task numbers well over one hundred, any attempt to acknowledge their individual contributions in the limited space available would be practically impossible.

The National Bureau of Standards Boulder Laboratories at Boulder, Colorado once again served as the host for the 1972 Cryogenic Engineering Conference. For the Cryogenic Engineering Conference it was like coming horne, for it was at the NBS Boulder Laboratories that the Cryogenic Engineering Conference was first conceived and held m 1954m connection with the dedication ofthe NBS Boulder Laboratories by President Dwight D. Eisenhower. The Cryogenic Engineering Conference IS grateful for the continuing support that the National Bureau of Standards has gIVen over the years, and which was expanded on July 1, 1971 when the NBS Boulder Laboratories assumed the secretariat function of the Conference from the National Academy of Sciences. Because of common interests in heat transfer, the 1972 Cryogemc Engineering Conference worked with the 13th National Heat Transfer Conference to develop a joint program m heat transfer. A majority ofthe papers presented in this cooperative effort are incIuded m V olume 18 of the Advances zn Cryogenic Engineerzng through the kmd permission ofthe 13th NatIOnal Heat Transfer Conference and are acknowl­ edged accordingly.