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. 99.2% of the photons, as measured by the pair spectrometer, are coming through the collimator holes.

• 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. 93% of the photons, as measured by the pair spectrometer, are coming from the radiator.

• 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)
• 135 cm is about 44 ns for 5 MeV neutron (10.3% of the speed of light)
• 135 cm is about 31 ns for 10 MeV neutron (14.6% of the speed of light)

TDC Calibration

NIM to ECHO translator channel 0

0.056689342404 ns per 1 channel
5.67 ns per 100 channel
56.7 ns per 1000 channel

Summary what was been done

Run #	Beam	Dump magnet	Collimator	Radiator	Target	Comments
2321	On	In	Open	In	No	R(upstream) = e+/pulse, R(downstream) = e+/pulse Pair-spectrometer rate measurements with collimator open
2322	On	In	Blocked	In	No	Pair-spectrometer rate measurements w/ collimator blocked w/ lead, 6" upstream, 4" downstream.
2323	On	In	Open	In	No	Repeat 321
2324	On	In	Open	Out	No	Study of radiator in/out effect by comparing w/ previous run.
2325	On	In	Open	In	D20	223A16(el) in TDC1 (-30 mV), PS upstr in TDC2 (-150 mV), PS downstr in TDC4 (-150 mV)
2326	On	In	Open	In	No	nothing
2327	On	In	Open	In	No	nothing
2328	On	In	Open	In	DU cylinder	-150 mV on 223A16(el)
2329	On	In	Open	In	DU cylinder	-60 mV on 223A16(el)
2330	On	In	Open	In	DU cylinder	same, but increased the current up to 240 mA. 0.1 Hz for neutrons
2331	On	In	Open	In	DU plate	DU target rotated by 45 deg vertically. Production run. TDC1:A16, TDC2:PSupstrm, TDC3:A17, TDC4:PSdstr, TDC5:A18, TDC6:A19, TDC7:A20, TDC8:A21, TDC9:A22, TDC10:A23, TDC11:A24
2332	On	In	Open	In	DU plate	TDC6 - nothing, TDC9 - need low threshold?, TDC10 - nothing
2333	On	In	Open	In	DU plate	nothing
2334	On	In	Open	In	DU plate	confirmed that TDC6 and TDC10 are bad. TDC6 -> TDC13, TDC10 -> TDC14
2335	On	In	Open	In	No	pair spectrometer rate and peak investigation. Thinking that: 1st peak - γ's and e±; 2nd - target, 3d - smth.
2336	On	In	Open	In	No	Capton e± converter in (0.864 mm)
2337	On	In	Open	In	No	Al e± converter in (3.1-3.2 mm)
2338	On	In	Open	In	No	same as before plus 31mm Al in front of e± detectors

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