Kevin Beard- Shedding FEL Light on Dark Matter: a simple experimentalist's view of the LIPSS experiment

8/3/2019 Kevin Beard- Shedding FEL Light on Dark Matter: a simple experimentalist's view of the LIPSS experiment

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Thomas Jefferson NationalAccelerator Facility

Shedding FEL Light on Dark Mattera simple experimentalist's view of the LIPSS

experiment

Kevin Beard for the LIPSS collaboration

FEL Users Group Meeting

May 16, 2007


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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)

LIght Pseudoscalar or Scalar Search


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A very brief history of dark matter...

M51

1933 Zwicky found that therotational speed of stars requiresmuch more mass than can be seen

1823 Olbers asked why the sky isdark at night

2006 NASA reports gravitationallensing from dark matter


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what might dark matter be?

baryonic matter -

very dim stars (MACHOs)

non-baryonic matter

hot dark matter ultra-relativistic (, ...)

warm dark matter relativistic

cold dark matter non-relativistic (WIMPs, axions,...)


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Many experiments looked for colddark matter......

PVLAS thinks theysaw something !

courtesy O.K.Baker


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courtesy O.K.Baker

Axion searches to date


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Axion and `Strong CP Problem

Peccei, Quin (1977); S. Weinberg (1978); F. Wilczek(1978)

courtesy A.Afanasev


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PVLAS experiment

courtesy of PVLAS:

http://www.ts.infn.it/physics/experiments/pvlas/

ellipticity plane to ellipticalpolarizaton

dichroism rotation of

polarization


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light shining through a wall

opaque

wall

light in light out

dark matterparticle

4 42

2

sin( /4 )

2 /4

b

b b

m LBL W R A

M m L

=


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BFRT* regeneration expt.

For (identical) magnets lengthL and fieldB, photon energy ,power W, efficiency , and detector sensitivityA, the rateR is:

4 42

2

sin( / 4 )

2 / 4

=

b

b b

B L m L W R A

M m L


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LIPSS apparatus.

Brewster windows

935

nm

isolated vacuumsystems

particle?

regenerated

light


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details of LIPSS layout (not to scale)


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.

Detector optics

Spec10:400BR-LNcamera

lensmirror


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What our camera sees...

1340 x 400 = 536000 (20 x 20 m) pixels


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#pixels

readoutnoise

dark current

cosmicrays,etc

1 second ADC counts/pixel

2 hour ADC counts/pixel

1340 x 400 = 536000 (20 x 20 m) pixels

bi i i i t t


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binning is important

1 X 1 5 X 5

1mm X 1mm regionbinning canbe done on chip beforereadout to minimize noise,but one must choose the binning wisely to optimize the signal


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actual power delivered to the LIPSS

dump over 5 days


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The beam spot driftedand had to be adjusted

using picomotors everyfew minutes. The spotswere logged to VHS

tape.

The picomotor control systemsometimes moved mirrors on

its own; this is an example ofdamage done by the laser.The beam also damaged &

vented our vacuum system the loss of vacuum wasn'timmediately noticed.

lessons learned...


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If you're looking for dark matter,

don't forget to turn off the lights....

temporary very high dark current area on CCD

Not sensitive enough yet to see a signal at the level


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all anomaly-free pixels

near region-of-interest

region-of-interest

Not sensitive enough yet to see a signal at the levelexpected on the basis of the PVLAS result

R C ifi


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Thomas Jefferson NationalAccelerator Facility 22

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 readnoise and dark current.

Our task is to get to a sensitivity that would enable thePVLAS boson hypothesis to be definitively confirmed orrejected .

courtesy of K.McFarlane


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Thomas Jefferson NationalAccelerator Facility 23

Preliminary result for Run C

The preliminary 3-sigma upper limit excludes

boson masses above 1.55 meV.

F t Pl


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Future PlansRun again with more power(~1 kW) usingimproved mirrors as soon as possible; take moredata in both pseudoscalar () and scalar ()configurations

Investigate other improvements or follow-onexperiments

Continue the quantum efficiency and uniformitymeasurements on the camera

Complete a thorough statistical treatment of thedata.

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Kevin Beard- Shedding FEL Light on Dark Matter: a simple experimentalist's view of the LIPSS experiment