Shedding FEL Light on Dark Matter a simple experimentalist's view of the LIPSS experiment
Kevin Beard for the LIPSS collaboration
FEL Users Group Meeting May 16, 2007
Thomas Jefferson National Accelerator Facility LIght Pseudoscalar or Scalar Search
A. Afanasev, C. Long, K.W. McFarlane, R. Ramdon, and H. Brown (Hampton University)
K. Beard, J. Boyce, G. Biallas, and M. Shinn (Jefferson Lab)
O.K. Baker and M. Minarni (Yale University)
Thomas Jefferson National Accelerator Facility A very brief history of dark matter...
1823 – Olbers asked why the sky is dark at night
1933 – Zwicky found that the rotational speed of stars requires much more mass than can be seen
2006 – NASA reports gravitational lensing from dark matter
M51
Thomas Jefferson National Accelerator Facility what might dark matter be?
• baryonic matter - – very dim stars (MACHOs)
• non-baryonic matter – hot dark matter – ultra-relativistic (ν,...) – warm dark matter – relativistic – cold dark matter – non-relativistic (WIMPs, axions,...)
Thomas Jefferson National Accelerator Facility Many experiments looked for cold PVLAS thinks they dark matter...... saw something !
courtesy O.K.Baker
Thomas Jefferson National Accelerator Facility Axion searches to date
courtesy O.K.Baker
Thomas Jefferson National Accelerator Facility Axion and `Strong CP Problem’
Peccei, Quin (1977); S. Weinberg (1978); F. Wilczekcourtesy A.Afanasev
(1978) Thomas Jefferson National Accelerator Facility PVLAS experiment dichroism – rotation of polarization
ellipticity – plane to elliptical polarizaton
courtesy of PVLAS: http://www.ts.infn.it/physics/experiments/pvlas/
Thomas Jefferson National Accelerator Facility light shining through a wall
dark matter particle light in light out
opaque
wall 44 2 ⎛⎞⎡B′′LWsin(mLb ′′ / 4ω ) ⎤ R=⎜⎟⎢ 2 ⎥ ηA ⎝⎠⎣2/4MmLbb′′ω ⎦ω
Thomas Jefferson National Accelerator Facility BFRT* regeneration expt.
For (identical) magnets length L′ and field B′, photon energy ω ′, power W, efficiency η, and detector sensitivity A, the rate R is:
44 2 ⎛⎞⎡BL′′sin( mb L ′ / 4ω ′ ) ⎤ W R = ⎜⎟⎢ 2 ⎥ ηA ⎝⎠⎣2/MmLbb′ 4ω′′ ⎦ω
Thomas Jefferson National Accelerator Facility Thomas Jefferson National Accelerator Facility LIPSS apparatus.
Brewster windows particl e?
regenerate 935 isolated vacuum systems d nm light
Thomas Jefferson National Accelerator Facility details of LIPSS layout (not to scale)
Thomas Jefferson National Accelerator Facility Detector optics
.
mirr lens Spec10:400BR-LNor camera
Thomas Jefferson National Accelerator Facility What our camera sees...
Thomas Jefferson National Accelerator Facility 1340 x 400 = 536000 (20 x 20 μm) pixels
dark current
cosmic rays,etc #pixels 2 hour ADC counts/pixel
readout noise
1 second ADC counts/pixel
Thomas Jefferson National Accelerator Facility binning is important
1 X 1 5 X 5 1mm X 1mm region binning can be done on chip before readout to minimize noise, but one must choose the binning wisely to optimize the signal
Thomas Jefferson National Accelerator Facility actual power delivered to the LIPSS dump over 5 days
Thomas Jefferson National Accelerator Facility lessons learned...
The picomotor control system sometimes moved mirrors on its own; this is an example of The beam spot drifted damage done by the laser. and had to be adjusted The beam also damaged & using picomotors every vented our vacuum system – few minutes. The spots the loss of vacuum wasn't were logged to VHS immediately noticed. tape.
Thomas Jefferson National Accelerator Facility If you're looking for dark matter, don't forget to turn off the lights....
temporary very high dark current area on CCD
Thomas Jefferson National Accelerator Facility Not sensitive enough yet to see a signal at the level expected on the basis of the PVLAS result
all anomaly-free pixels
near region-of- interest
region-of- interest
Thomas Jefferson National Accelerator Facility Run C specifics
• Run C was the first run with adequate monitoring • Aquired a good set of data with polarization || to magnetic field; need a similar set with the polarization ┴ to the magnetic field • ~12 MJ of photons were delivered in 12 good 2-hour runs • The only detectable sources of uncertainty were read noise and dark current. • Our task is to get to a sensitivity that would enable the PVLAS boson hypothesis to be definitively confirmed or rejected .
courtesy of K.McFarlane
Thomas Jefferson National Accelerator Facility 22 Preliminary result for Run C
The preliminary 3-sigma upper limit excludes boson masses above 1.55 meV.
Thomas Jefferson National Accelerator Facility 23 Future Plans •Run again with more power (~1 kW) using improved mirrors as soon as possible; take more data in both pseudoscalar (┴) and scalar (║) configurations
•Continue the quantum efficiency and uniformity measurements on the camera •Complete a thorough statistical treatment of the data. •Investigate other improvements or follow-on experiments
Thomas Jefferson National Accelerator Facility