September 8, 2011

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Thursday Run Plan (blue is done)

• Push dump magnet upstream as far as possible

• Shield around it with lead as far downstream as possible. (Last time, this helped a lot.)

• Calibrate TDC

• Get a TOF spectrum with the D2O target. Set detector thresholds.

• Verify that most of the photons, as measured by the neutrons from D2O and the pair spectrometer, are coming through the photon collimators. Do this by looking at both count rates for radiator in and photon hole blocked and unblocked. 91.2% of the photons are coming through the collimator!

• Initiate studies of backgrounds, where “background” is defined as photons not coming from the radiator. Do radiator in/radiator out runs for beam on central position. Look at count rates for both neutrons from D2O and pair spectrometer.

• Check for time stability of ratios of backgrounds to good stuff.

• Do background studies (radiator in/out) for beam up and beam down.

• Evaluate if hardener is useful. If so, optimize thickness.

• Do D2O asymmetry measurements.

some notes

• neutron rest mass is about 940 MeV
• 1 ns speed of light is about 30 cm. So
• 135 cm is about 4.5 ns for gamma

neutron TOF calculation in non-relativistic limits:

• 135 cm is about 136 ns for 0.5 MeV neutron (3.3% of the speed of light)
• 135 cm is about 98 ns for 1 MeV neutron (4.6% of the speed of light)
• 135 cm is about 69 ns for 2 MeV neutron (6.5% of the speed of light)
• 135 cm is about 60 ns for 3 MeV neutron (7.9% of the speed of light)
• 135 cm is about 49 ns for 4 MeV neutron (9.2% of the speed of light)

TDC Calibration

NIM to ECHO translator channel 0

(0.056689342404 ns/channel)

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