16/03/2023

Plunger chamber closed, some dummy target and stopper probably inside

run 72    eagle closed

run 73    right half of EAGLE completely opened

Three screenshots are attached:

Run 72  EAGLE closed

1)  Three rings.  There is significantly more 511 in ring 143 than in 117, 101

2) 5 detectors of ring 143. They all look similar to each other.

Run 73  right half of EAGLE opened

3) 5 detectors of ring 143.  The 3 detectors in the opened half hardly see 511 keV, the other 2 do.

Check with Colibri and a gamma scintillator probe ws done: largest activity is visible close to the target chamber, in the region starting at the edge of the chamber, end ending about 6 cm upstream.

About 80 gamma counts/s are seen there. The count rate decreases further upstream.

Background rate:  20 to 30 counts/s, 25 counts/s in Sala Fizykow.

Radioactivity line seen in the spectra,  with the same behaviour as 511:   743.5,  936 keV, 1434 keV.  These are lines from 52Cr, fed by beta+ decay of 52Mn.

Confirmed by Michain gamma-gamma.

52Mn can be produced in the a2pn channel in  the reaction 32S+27Al