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					An Aspect of Dark
     Matter
   You Wouldn’t
NORMALLY Think Of
Even If It Wasn’t Frank
 and Ettore’s Birthday
                                       Practical ∗
                              Applications????




*   Who do you think you’re kidding?
Well,




                               Think Cracks ∗




*   Who hasn’t had problems with them?
              First runs of
  CRESST Cryogenic Dark Matter Detector
             in Gran Sasso

 Much careful effort– Expect: few events/day

          Horror–Find: 1000’s /hour

Several months, crazy hypotheses (touched with
          hands? traffic in tunnel?...)

Even an unknown Background is Poisson in time

  But not Poisson –come in ‘Bursts’– so not
         radioactive contamination.

           Whaaaat the Devil is it?
                 The Culprit!!




Sapphire crystal surface, contact point with sapphire ball
          Happy ending:
Replace hard sapphire support balls
     with softer plastic stubs


 Rate goes down to expected level


              WHEW


            Conclusion
     Events were all “Cracks”
Several years later...early one morning (11:AM)...




                    Hey!


We must have the worlds’ greatest collection of




            Crack Data
Good energy, time measurement, low background

     Tens-hundreds of thousands of events

              Anybody interested??
Several years later... Finland ( 11:AM, Jyvaskala )

                                                  YES !

                       10000




                       1000
  No. events per keV




                        100




                         10




                          1




                         0.1
                               1             10                    100   1000
                                                    Energy (keV)

                                   Energy spectra from four runs


                                     Just like earthquakes,

                                                  E −β

                          Even about same power β ≈ 1.7 − 2.0
                          Except we really know energy, EQ’ers don’t.
Richter scale is an amplitude and with only small part of total energy.
                                   But EQ data has much larger range
                                       Many plots, correlations

                                            Waiting Times

                        1e+08




                        1e+07




                        1e+06
no. events per unit w




                        100000




                         10000




                         1000




                          100
                            1e-04             0.001                           0.01   0.1
                                                      waiting time w in hrs

                                 Upper:Cracks; Lower: Calibration photons


                                         Cracks: w−αe−w/wo
                                      Photons: e−w/wo (Poisson)

                        Also found for earthquakes, about same power
                                            α ≈ 0.3
                                             (poorly determined)
                      Conclusions

   • New Technology for Studying Microfracture
   Unparalled sensitivity. Perhaps to few atom level with
                         dedicated setup

             Many 10x better than previous technology




             • Striking parallels with EQ’s
   Stupendous energy range! And big material differences

 Something universal must be going on. Relations between
                        exponents, α, β?


      • Absolute measurement of total energy

                 • Large clean data sets.
     Look for patterns, “percursors” of ‘Big Events’ ?
    (So far we couldn’t find an effective ’EQ predictor’ algorithm)


   • Reference: ‘Fracture Processes Observed With A
Cryogenic Detector’, J.Astrom et al., arXiv:physics/0504151;
                Phys. Lett.A356 262 (2006).
       (Also arXiv:physics/061208, arXiv:0708.4315)
Mass Spectroscopy of
  Macromolecules


 Or,... one of Leo’s
  deepest physical
     insights...
20 keV = 20 keV ! !
       Usual detectors need velocity

  In genomics, proteomics,..biologists will have
 fragments in kiloDaltons (Dalton= 1 H atom)
              accelerator ∼ 20keV .

      Since E = 1 M v 2, molecule is slooow.
                2


 With practically all familiar detectors, initiating
          event is hitting an electron.

      This depends on velocity (max when
v(projectile) ≈ v(atomic electron)) and it becomes
          difficult and inefficient for e.g.
                    big proteins.
    Cryodetector needs energy (Heat)

For a cryodetector a huge, slow, 20 keV protein
       is the same as a 20 keV electron !?

 So ask (1991) Marvin ( brother microbiologist).
         Marv to Leo: Maybe interesting

    Discusions, finally actually carried out by
           Damien Twerenbold et al.

                     Works!!

We have since seen up to 100 000 Dalton proteins



  Also very high sensitivity, good timing reduces
                   background



                Below Attomoles
                     Conclusions




• For cryodetector really true that 20keV ≈ 20keV !

         • In principle no mass limitation

                • Very high sensitivy
         Rare protein studies and diagnostics,...


    • Good timing gives high mass resolution
          Could see deuteration of single base?


 • References: D. Twerenbold et al, Appl. Phys.
             Lett. 68, 3503 (1996);
    P. Christ et al. European Journal of Mass
        Spectrometry 10, 469-476 (2004)

				
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posted:10/24/2012
language:English
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