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ALSNews           Vol. 75           April 16, 1997

Table of Contents


    1. OPERATIONS UPDATE
    2. SYNCHROTRON RADIATION TURNS THE BIG FIVE-O
    3. PHONE NUMBERS ON ALS FLOOR TO CHANGE

1. OPERATIONS UPDATE
(contact: rmmiller@lbl.gov)

Operations Summary for April 16 - April 28

Apr 16, 00:00-08:00           User scrubbing & special operations
Apr 16, 08:00- Apr 21, 07:15  1.5-GeV/400-mA/288-bunch user operations
                              with "camshaft" fill pattern
Apr 21, 07:30-24:00           Maintenance & startup
Apr 22, 00:00-24:00           Accelerator physics
Apr 23, 00:00-08:00           User scrubbing & special operations
Apr 23, 08:00- Apr 27, 24:00  1.9-GeV/400-mA/288-bunch user operations
                              with "camshaft" fill pattern

On April 28, the ALS will begin a shutdown for equipment installation and maintenance. (For details, see ALSNews Vol. 74, April 2, 1997.) User beamtime is scheduled to resume on June 10.

Weekly operations scheduling meetings are held on Fridays at 3:30 p.m. in the Building 6 conference room. The Accelerator Status Hotline at (510) 486-6766 (ext. 6766 from Lab phones) features a recorded message giving up-to-date information on the operational status of the accelerator.

2. SYNCHROTRON RADIATION TURNS THE BIG FIVE-O

Synchrotron radiation was first observed by a General Electric technician on April 24, 1947, and was for years thereafter a footnote in the history of science that attracted little attention. But, as in the case of a problem child who grows up to do something worthwhile in later years to everyone's surprise, we now like to recount the childhood biography of this special form of light that has turned out to be so useful.

The story is inextricably linked with the dynamic evolution of nuclear physics throughout the 20th century and in particular with the development of particle accelerators during the 1930s and 40s. As in all good stories, there's a cosmic angle-synchrotron light as a form of starlight has been around since time began. And there are giants in the land-scientific giants the likes of Maxwell, Bohr, and Rutherford, among others. Each played a role through his work to understand the nature of subatomic particles, contributing to the development of high-energy particle accelerators, the drama in which synchrotron radiation began as an unwelcome subplot.

When, by the mid-40s, particle accelerators had reached the energies that could accelerate charged particles to relativistic speed and mass, the fact that they turned into big, expensive light bulbs in the process posed then and still poses today challenging technological hurdles. Charged particles forced by magnetic fields into circular orbits emit large quantities of photons, and this loss of radiation energy was viewed by particle physicists for many years as a waste and even a disposal problem. But back in 1944, it was more than that. While it was still theory rather than fact, it seemed that it might be the Achilles' heel of high energy physics research, and that's where we'll jump into the story.

It was in D.W. Kerst's betatron, which he had invented in 1940 at the University of Illinois, that the theory leaped inevitably toward fact. Building on E.O. Lawrence's idea of the proton-accelerating cyclotron, Kerst introduced the idea of accelerating electrons in circular orbits by using a changing magnetic field to produce an accelerating electric field, which served to achieve electron energies of 2.3 MeV.

Although radiation loss by accelerated electrons was negligible at this stage, the Soviet scientists D. Ivanenko and I. Pomeranchuk were quick to point out in a letter to Physical Review the implications of Kerst's design: they predicted that energy lost through electromagnetic radiation would place an upper limit on the particle energy a betatron could achieve (Phys. Rev. 65:343, 1944). Although this wasn't exactly a new idea (the year after the electron was discovered, Lienard in 1898 had theorized that an orbiting electric charge should radiate electromagnetic energy, even though the phenomenon had never been verified experimentally and was by the 1930s a textbook footnote), new circumstances had at last made it relevant to the business at hand.

Shortly after the letter was published, General Electric had under construction a 100-MeV betatron in Schenectady, New York, which was a large induction accelerator for x ray and nuclear research. When it came online, a G.E. physicist, J.P. Blewett, undertook in 1945 the first systematic search to verify Ivanenko and Pomeranchuk's predictions. He didn't succeed in observing the emitted electromagnetic radiation, although he showed that the electrons' orbit contraction was consistent with their predicted radiation loss. J. Schwinger's calculations of classical (i.e., nonquantum) radiation loss by accelerated electrons, available at the time but not published until 1949, made it clear Blewett had looked in the wrong part of the electromagnetic spectrum. At 100 MeV the signal would be found in the near infrared or the visible region. Were it not for the fact that Blewett searched in the radiofrequency region and the betatron's vacuum chamber was opaque, we would be celebrating the 52nd anniversary of Blewett radiation.

In the meantime, accelerator development was taking another tack on the West Coast and in Europe. In a letter to Physical Review in 1945, E.M. McMillan at UC Berkeley, and, independently, V.I. Veksler in the Soviet Union, proposed a new type of accelerator, now known as the synchrotron (Phys. Rev. 68:144, 1945). GE physicists in Schenectady were ready to run with the idea and design the prototype, since during the war they had worked with Lawrence and the Berkeley community of physicists on the Manhattan Project and were poised in 1946 to construct a new 70-MeV machine to test Vecksler and McMillan's synchrotron principle (along with other design elements that would lead to a reduction in accelerator size and expense). This first synchrotron had been designed with a transparent glass vacuum tube, and it is for this reason that the light that would be named synchrotron radiation was discovered on April 24, 1947. It was a technician who first noticed what he thought might be sparking in the tube from one of the pulse transformers. No one knew exactly what the glowing light was at first, but soon it became clear that it was the radiation Ivanenko and Pomeranchuk had predicted, and in the visible range, just where Schwinger said it would be at this energy. This first light had at last proven the theory and through historical serendipity this "new" form of radiation was christened with the name it carries to this day.

3. PHONE NUMBERS ON ALS FLOOR TO CHANGE

During the April-May shutdown, telephone numbers on the ALS floor will change. The switch results from the introduction of a new prefix for Berkeley Lab phones. Because the laboratory is running out of numbers beginning with 486, new telephone numbers will be given the prefix 495. The extensions will range from 2000 to 2999. To keep all extensions unique, the few telephone numbers between 486-2000 and 486-2999 that have already been assigned will be changed to new extensions with the new prefix. This affects all telephones on the ALS floor as well as the fax machine (which was recently upgraded with more memory to handle larger documents). Once a phone number has been changed, callers will hear a message telling them what the new number is. Calls to the old fax number will be forwarded to the new fax number for two months following the changeover. The new beamline telephone numbers are as follows:

Beamline   Old Extension   New Extension
Number        (486-)          (495-)

3.1            2931            2031
5.0.2          5855            2052
6.1            2961            2061
6.3            2963            2063
6.3            2964            2064
7.0            2970            2070
7.0            2971            2071
7.0            2979            2079
7.3.1          2972            2072
7.3.1          2973            2073
7.3.3          2974            2074
8.0            2980            2080
8.0            2989            2089
9.0.1          2990            2090
9.0.1          2991            2091
9.0.2          2992            2092
9.3.1          2994            2094
9.3.2          2993            2093
9.3.2          2909            2109
10.3.1         2903            2103
10.3.1         2904            2104
10.3.2         2905            2105
10.3.2         2906            2106
12.0           2900            2120
12.0           2901            2121

Fax            2930            2130

If you are not currently subscribing to ALSNews and wish to receive it by electronic mail, send your internet address to ALSNews@lbl.gov. We welcome suggestions for topics and content. Writers: deborah_dixon@macmail.lbl.gov, jccross@lbl.gov, annette_greiner@lbl.gov, kdevereaux@lbl.gov