Fe55 peak shape

Fe55 with 50/50 Ar/CO₂, New preamp and new HVB, ADC half-range

Mixed 50/50 at 40 sccm total, moved the source (collimated as usual) across the top of the straw towards the edge.... With the source over the edge of the straw, the count rate halves and the camel disappears.

max amplitude histo for 55Fe mixed 50/50 at 40 sccm

energy histo for 55Fe mixed 50/50 at 40 sccm

max amplitude histo for 55Fe (side of straw) mixed 50/50 at 40 sccm

energy histo for 55Fe (side of straw) mixed 50/50 at 40 sccm

Overlaying side and edge data, the light coloured plots are with the source above the wire.

max amplitude histo for 55Fe mixed 50/50 at 80 sccm

energy histo for 55Fe mixed 50/50 at 80 sccm

Repeated at 60 sccm

max amplitude histo for 55Fe mixed 50/50 at 60 sccm

energy histo for 55Fe mixed 50/50 at 60 sccm

Events histograms with the source above the wire.

55Fe events, mixed 50/50 at 60 sccm, 1850V

55Fe events, mixed 50/50 at 60 sccm, 1950V

55Fe events, mixed 50/50 at 60 sccm, 2050V

Events histograms with the source off the wire (above the edge of the tube).

55Fe events, mixed 50/50 at 60 sccm, 1850V

55Fe events, mixed 50/50 at 60 sccm, 1950V

55Fe events, mixed 50/50 at 60 sccm, 2050V

90/10 Ar/CO₂ (premixed) at approx 80 sccm
The light coloured plots were produced with the 55Fe source centred over the wire; for the darker plots the source was close to the side of the tube. The operating voltage for that mix was previously chosen to be 1450V. Afterpulses are present at 1550V (delayed, so are not included in the integration). The count rate decreased by approx 1/3 when moving the source to the side of the tube - with the 50/50 gas mix the count rate decreased by at least 1/2.