The Synchrotron Light Monitor Laboratory at SSRL, SLAC national accelerator laboratory  

The primary function of the SSRL synchrotron light diagnostic laboratory is to study and monitor the physical properties
of the relativistic electron bunches circulating in the storage ring of SPEAR 3 in various electromagnetic environment as
result created by the geometry of the beam tube, beam shaping magnets, charge injection method and electron density
distribution in the bunch.

The synchrotron light of the diagnostic beam line is generated
by accelerating the electron bunches through a dipole magnet.
The synchrotron emission from individual bunch spreads out in a
cone of white light with X-ray at the centerand visible light fanning
out at the outer edge of the cone. A cold finger is placed at the
center of the beam to block off the X-ray allowing the visible light
above and below the cold finger to propagate to the detector.  
The figure on the right shows the spectrum of the visible synchrotron
light dispersed with a prism. The dark band at the center is the
shadow cast by the cold finger.(Ref. 3, 5, 8)

The major optical set up in the lab consists of:

  •  A Hamamatsu streak camera to measure the longitudinal
   profile of the synchrotron light pulses (Ref.4,8)
  •  A PiMax fast gated camera to measure images of the
   beam cross-section (Ref.2)
  •  An interferometer to measure the micro dimension of
   the relativistic electron bunch (Ref.1)
  •  Avalanche photo-diode to study the beam fluctuation
  •  A High speed rotating mirror image scanning set up
   to study the long range temporal effect (Ref.2)

A brief History

SSRL visble light diagnostic laboratory was the brainchild of Bob Hettel, Deputy director of SLAC. Jeff Corbett and
Walter Mok  from LIFEIT started their collaboration in the summer of 2004, and did most of the laboratory build-up
during the Christmas Holiday of 2004. After passing the stringent safety requirements, the first visible light was seen in
April 2005 (reported by SLAC today, see picture above).  Since then, the laboratory set up becomes one of the
indispensable tools for accelerator physics research.  

Prior 2004, Bob Hettel proposed and initiated the construction of the visible beam line. Jeff Corbett, Cecil Limborg
              and Andy Ringwall designed the beam line.
2004, Jeff Corbett and Walter Mok of LIFEIT built the SSRL optics lab during the Christmas Holiday.
2005, The first visible light came out of the SPEAR 3 electron storage ring.
2006, Commissioning of the beam line
2007, Operation of the Streak Camera,
      Jeff and Walter attended T Mitsuhashi 's class on beam size measurement at KEK, Japan, in the summer.
2008, Alan, Jeff and Walter taught the first course on visible synchrotron light diagnostics, with lab experiment, at   
      USPAS 2008, United States Particle Accelerator School.
      T Mitsuhashi, Jeff Corbett, and Walter Mok gave a one week beam diagnostic seminar at SSRL
      the Shanghai Synchrotron Radiation Light source.     
2009, Conducted the first interferometer beam size measurement in SPEAR 3.
      Studied beam dynamics with a Fast Gated camera.
2010, Alan, Jeff, Walter and Wexing taught a course on Visible synchrotron light diagnostics at USPA 2010.
      Collaborated with Professor Aaron Lindenberg on ultrafast phenomena       

Publications (Reference)

  •  1. Interference beam size measurement in SPEAR 3 PAC 2009, Vancouver, Canada.
  •  2.Fast gated camera in SPEAR 3, PAC 2009 Vancouver, Canada.
  •  3.Spear 3 accelerator physics update. PAC 2007, USA
  •  4.Bunch length measurement in SPEAR 3, PAC 2007 Albuquerque, USA
  •  5.Commissioning the SPEAR 3 diagnostic beam line EPAC 2006, Edinburgh, Scotland
  •  6.Streak camera measurements with high currents in PEP II and variable optics in SPEAR 3, BIW 2008, Tahoe City
  •  7.Bunch Length and impedance measurements at SPEAR 3, EPAC 2008, Genoa, Italy
  •  8.The SPEAR 3 Diagnostic beam lines, PAC 2005 Knoxville, Tennessee, USA.


First and foremost, we owe our indebtedness to Bob Hettel, Deputy Director of SLAC, who initiated the project and
continued his unwavering support for the visible beam diagnostic laboratory.  Jeff's perseverance and generous spirit of
collaboration have been the foundation of putting together such an inclusive and diverse team of talents to perform all
these seemingly impossible tasks. For the Streak camera operation, we are grateful to the generous support in
instrument loan and sharing of valuable operating experiences from Alan Fisher of SLAC, Alex Lumpkin of ANL, Wexing
Cheng of Brook Haven, and F Sannibale of ALS.  We are mindful of the creative inquisitions from J. Safranek, X. Huang,
J. Seebeck, John Schmerge, and Aaron Lindenberg, from whom the Synchrotron Light Diagnostic laboratory would not
run out of challenge to meet.


SPEAR3 - Stanford Positron Electron Asymmetric Ring is an electron storage ring to generate synchrotron light.
Shown below is the Stanford
Synchrotron Radiation Light
( Ref.2 )
( REF. 4 )

RESEARCH at the SLAC national accelerator laboratory.

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