Proton Calorimetry/Experimental Runs/2017/September7

Beam tests of the Nuvia 10 mm, 4 mm and 3 mm scintillator sheets with PRaVDA CMOS pixel sensors (PRIAPUS) at the Birmingham Cyclotron with a 28 MeV beam.

Pre-data Taking Information and Notes

• The tests were carried out with an energy of 28 MeV (32 MeV was unavailable as the cyclotron had recently been through repairs). No Bragg Peak measurement was carried out to confirm the exact beam energy due to time restrictions.
• The beam was run without a scattering foil. A 1 cm diameter uniform beam was achieved by placing a 1 cm collimator in the beam, with a beam scan onto film confirming the size. An ionisation chamber was placed upstream of the collimator to accurately monitor the current.
• The dynamic range of the CMOS sensors is 14 bits. The electron conversion value from ADC is 50 electrons per ADC value. The measurements to establish this were carried out at the beginning of experimentation with the sensors and this value may have changed due to radiation damage etc.
• From previous measurements, the average background value per pixel is ~ 700.
• The data was recorded at 45 frames/second.
• The scintillator stack was set up perpendicular to the proton beam, with the exposed sides of the scintillator facing the sensors:

• The scintillator stack was quite well aligned with the horizontal centre of the beam. We did our best to align the vertical centre of the scintillator stack with the beam as well, however as can be seen from the image below, where the black "line" shows the divide between and hence the centre of the sensors, the beam hit just below centre:

• The working directory on the PRIAPUS computer where the data is stored is:

idMateData\Bham070917\

• The directory the data is stored at UCL in is:

/unix/pbt/data/birmingham/sept_2017

Data Taking

Type of run	Current	Scintillator sheets used	Scintillator arrangement	Notes	File name
Background	N/A	3 x 3 mm	ABC	Background ADC count slightly higher than usual Tiles are grouped together in a tight formation (until mentioned otherwise)	Background_1
Beam	1 nA	3 x 3 mm	ABC	Saturation of sensor, ADC values at 14,000	28MeV_3mmscint_ABC_1nA_1cmC
Beam	0.1 nA	3 x 3 mm	ABC	Current reduced by a factor of 10 Beam dropped during run	28MeV_3mmscint_ABC_100pA_1cmC_1
Beam	0.1 nA	3 x 3 mm	ABC	Saturation of sensor	28MeV_3mmscint_ABC_100pA_1cmC_2
Beam	10 pA	3 x 3 mm	ABC	Sensor no longer saturated, but no separation due to formation of tiles	28MeV_3mmscint_ABC_10pA_1cmC
Beam	10 pA	3 x 3 mm	ABC	Due to gap between the sensor and the scintillators there is an overlap in the light collected by the sensor and no separation of the scintillators can be seen In order to see some separation, place the scintillators with a gap of ~ 1-2 cm between each sheet This setup remains in place until mentioned otherwise Lights were left on for the first run. Data not useable!	28MeV_3mmscint_ABC_spread_10pA_1cmC
Beam	10 pA	3 x 3 mm	ABC	Lights off this time!	28MeV_3mmscint_ABC_spread_10pA_1cmC_2
Beam	10 pA	3 x 3 mm	ABC	Repeat measurement for reproducibility	28MeV_3mmscint_ABC_spread_10pA_1cmC_3
Beam direction	N/A	N/A	N/A	Measure the direction of the beam relative to the screen by shining a laser on the sensor to make sure we understand the Bragg Peak that we see Saturation of the sensor	Laser_beam_direction
Beam direction	N/A	N/A	N/A	Cover some of the sensor not to saturate it Beam direction determined to be (for the top panel display): SCREEN <--- BEAM (where the arrow represents the direction of the beam)	Laser_beam_direction_cover
Beam	10 pA	4 mm and 3 mm	3A 4A	Alignment: 4A [gap] 3A <--- BEAM Lights were left on for this run. Data not useable!	28MeV_3mmA_4mmA_spread_10pA_1cmC
Beam	10 pA	4 mm and 3 mm	3A 4A	Lights off this time!	28MeV_3mmA_4mmA_spread_10pA_1cmC_2
Beam	10 pA	4 mm and 3 mm	3A 4A	Repeat measurement for reproducibility	28MeV_3mmA_4mmA_spread_10pA_1cmC_3
Beam	10 pA	3 mm and 4 mm	4A 3A	Scintillator plates switched around Alignment" 3A [gap] 4A <--- BEAM	28MeV_4mmA_3mmA_spread_10pA_1cmC
Beam	20 pA	3 mm and 4 mm	4A 3A	Continue with this configuration and increase current until we get to the maximum current that won't saturate the sensors First, double the current	28MeV_4mmA_3mmA_spread_20pA_1cmC
Beam	25 pA	3 mm and 4 mm	4A 3A	Increase current to 25 pA Possible saturation of sensors	28MeV_4mmA_3mmA_spread_25pA_1cmC
Beam	20 pA	3 x 3 mm	ABC	The maximum current before saturation is ~ 20 pA Repeat tests with 3 scintillator plates at this current Alignment: 3C [gap] 3B [gap] 3A <--- BEAM Lights were left on for this run. Data not useable!	28MeV_3mmscint_ABC_spread_20pA_1cmC
Beam	20 pA	3 x 3 mm	ABC	Lights off this time! The file preview showed that there is a tilt observed in the resulting data. This was caused by scintillator A tilting to the right in real life, as show in the below picture, which was taken just after the data run was taken:	28MeV_3mmscint_ABC_spread_20pA_1cmC_2
Beam	20 pA	3 x 3 mm	BCA	Alignment: 3A [gap] 3C [gap] 3B <--- BEAM	28MeV_3mmscint_BCA_spread_20mA_1cmC
Background	N/A	3 x 3 mm	BCA		Background_2
Beam	20 pA	3 x 3 mm	BCA	Alignment: 3A [gap] 3C [gap] 3B <--- BEAM Blue tack used to keep scintillator plates straighter and test repeated with the same alignment. Lights were left on for this run. Data not useable!	28MeV_3mmscint_BCA_spread_20mA_1cmC_2
Beam	20 pA	3 x 3 mm	BCA	Lights off this time!	28MeV_3mmscint_BCA_spread_20mA_1cmC_3
Beam	20 pA	3 x 3 mm	CAB	Alignment: 3B [gap] 3A [gap] 3C <--- BEAM! The tiles remained straighter for this run!	28MeV_3mmscint_CAB_spread_20pA_1cmC
Beam	20 pA	3 mm and 4 mm	4A 3A	Alignment: 3A 4A <--- BEAM	28MeV_4mmA_3mmA_spread_20pA_1cmC
Beam	20 pA	3 mm and 4 mm	4B 3A	Alignment: 3A 4B <--- BEAM	28MeV_4mmB_3mmA_spread_20pA_1cmC
Beam	20 pA	1 x 10 mm	10 A	Data taking resumed after short lunch break (in case this is of any relevance to any change in data caused by the beam being switched off for a short while) Alignment: 10A <--- BEAM	28MeV_10mmA_20pA_1cmC
Background	N/A	1 x 10 mm	10A		Background_3
Beam	20 pA	1 x 10 mm	10B	Alignment: 10B <--- BEAM	28MeV_10mmB_20pA_1cmC
Beam	10 pA	1 x 10 mm	10B	Decrease the current by a factor of 2 until we don't see anything above background	28MeV_10mmB_10pA_1cmC
Beam	5 pA	1 x 10 mm	10B	Current decreased by another factor of 2	28MeV_10mmB_5pA_1cmC
Beam	2.5 pA	1 x 10 mm	10B	Current decreased by another factor of 2	28MeV_10mmB_2-5pA_1cmC
Beam	1.25 pA	1 x 10 mm	10B	Current decreased by another factor of 2	28MeV_10mmB_1-25pA_1cmC
Beam	20 pA	1 x 10 mm	10B	Current brought back up to 20 pA 10 repeats of 1 second frames recorded, with _1, _2 etc. appended to file name Current dropped off slightly during acquisition	28MeV_10mmB_20pA_1cmC_repeat
Beam	20 pA	1 x 10 mm	10B	The setup has been moved off-centre to check for uniformity, with the beam hitting the right edge of the scintillator (when looking into the beam) The beam was also checked with a film placed on the scintillator to make sure the beam was hitting, and not missing, the scintillator 10 repeats of 1 second frames recorded, with _1, _2 etc. appended to file name	28MeV_10mmB_20pA_1cmC_right
Beam	20 pA	1 x 10 mm	10B	Plate 10B was removed from the stand and brought closer to the sensor to reduce the gap between the scintillator and the sensor to ~ 2mm at the bottom (and the gap slightly increasing towards the top, so the scintillator leans away from the sensor as it gets to the top of the sensor) Very saturated data!	28MeV_10mmB_20pA_1mcC_close
Beam	10 pA	1 x 10 mm	10B	Reduce current by factor of 2 Still see some slight saturation	28MeV_10mmB_10pA_1mcC_close
Beam	7 pA	1 x 10 mm	10 B	Further reduce current No saturation seen	28MeV_10mmB_7pA_1cmC_close
Beam	7 pA	3 x 3 mm	ABC	3 scintillator plates brought close to the sensor, taped together for stability so therefore without any separation Alignment: 3C [gap] 3B [gap] 3A <--- BEAM	28MeV_3mmscint_ABC_7pA_1mcC_close
Beam	5 pA	3 x 3 mm	ABC	Current dropped to 5 pA in hope of seeing more separation with less light	28MeV_3mmscint_ABC_4pA_1mcC_close

Conclusions

• A very successful first test beam at Birmingham, where we could see the Bragg Peak when using two plates (3 mm and 4 mm):

• Simulations were carried out of a 28 MeV proton energy and a 5 mm radius beam, with 10,000 events. The resulting energy deposited and the stopping distance can be seen below:

The stopping distance is ~ 6.1 mm, according to simulations. This agrees with the test beam where the Bragg peak is seen as two points in two plates totalling up to a total of 7 mm of scintillator.

• Full data analysis still to be carried out!