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The CF4 puzzle

The CF4 puzzle. Thanks to Dan Burke (after his videophone talk 20/12/05). The facts. CF4 has been used many times in Saclay It is used in several experiments (MuNu in Europe, a NP experiment in Japan…)

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The CF4 puzzle

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  1. The CF4 puzzle Thanks to Dan Burke (after his videophone talk 20/12/05) P. Colas - The CF4 puzzle

  2. The facts • CF4 has been used many times in Saclay • It is used in several experiments (MuNu in Europe, a NP experiment in Japan…) • Atempts to use Ar CF4 in the MPI chamber encountered problems : apparent loss of electrons (bad spectrum), instability, apparently reduced drift velocity (may be linked to afterpulses, a reanalysis of Carleton data seems to solve the problem for them) P. Colas - The CF4 puzzle

  3. The facts Saclay T2K Normal 55Fe peak seen at Saclay, resolution as expected KEK MPI-TPC Seem to loose electrons on the mesh (?), but photon rate OK (Paul and Vincent : attachment on the mesh, due to resonance – negative ions very slow, then stripped) (Yannis : UV photons back-scattered) P. Colas - The CF4 puzzle

  4. The facts Drift velocity about 8 cm/microsecond at E=220 V/cm, OK with Magboltz Drift velocity seems about 3 cm/micros at 80 V/cm, half than expected P. Colas - The CF4 puzzle

  5. The facts However disagreement on resolution with MC for Saclay cosmic data. Though perfect agreement for ArCH4 and Ar iso Something happens No after pulses, but pulse shape (STAR elec) not as beautiful as in other gases P. Colas - The CF4 puzzle

  6. CF4 – AfterPulses Typical track with after-pulses continuing for entire recorded time P. Colas - The CF4 puzzle

  7. CF4 – AfterPulse – Pulse Separation Separation time between individual after-pulses P. Colas - The CF4 puzzle [80 ns time bins]

  8. CF4 – AfterPulse – Pulse Separation Separation time between individual after-pulses P. Colas - The CF4 puzzle [80 ns time bins] [80 ns time bins]

  9. CF4 – AfterPulse Analysis Occasional far-pulses can be seen as far away as 2-3 cm from track P. Colas - The CF4 puzzle

  10. CF4 - AfterPulse Time separation between first pulse and later pulses in 80ns bins First-Second First-Third First-Fourth First-Fifth P. Colas - The CF4 puzzle

  11. CF4 - AfterPulse Amplitude of pulses wrt time (80ns bins) with first pulse normalized to 1.0 [80 ns time bins] P. Colas - The CF4 puzzle

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