Effects of Magnetic field on Voltage response of PMT

Transcription

1 Effects of Magnetic field on Voltage response of PMT Supervised by: Prof. Tsutomu Mibe Nitin, Parth, Sumukh KEK 31 st May 2017 Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

2 Outline 1 Introduction and Motivation 2 Overview of the Setup 3 Experiments Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

3 Introduction and Motivation The electrons travel to the output by bouncing through the Dynodes and multiply themselves. The trajectory of the electrons is important for the multiplication value. In the g-2/edm experiment for circular movement of the muons, we use a magnetic field. This would affect the PMTs in the setup used to count the number of muons in the beam. The material for shielding is costly hence it is necessary to know whether it is required and in what quantity before the experiment begins. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

4 Diagram of PhotoMultiplier Tube Figure 1: Schematic of PMT Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

5 Setup Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

6 Parts of the setup Solenoid Coils : Two coils wound around two halves of the bottle in series. Each half has dimensions 8cm x 9.5cm x 9.5cm. Each coil has turns of insulated copper wire of diameter 0.50mm. A total magnetic field of 10 Gauss was achieved at the centre of the setup with a current of 0.5 A in the coil. The current value was chosen as 0.5A to reduce heating in the coil, and number of turns in the coil was determined by approximating the field at the centre to be due to two cylindrical solenoids. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

7 Parts of the setup Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

8 Parts of the setup PMT : Hamamatsu H PMT was placed at the center of the coil for calibration in the presence and absence of magnetic field. LED driving circuit : The driving circuit was made with the following parts : A UV LED (UV3TZ ) A BJT (C1359) to act as a switch A pot of range 0 500Ω, to control the intensity of the UV LED Resistances - 1KΩ (1) and 30KΩ(1) Function Generator A square wave pulse of frequency 10 Hz and duty cycle 0.001% (pulse width of 1 microsecond) is generated and supplied to the base of the transistor by a Function Generator. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

9 Parts of the Setup (a) Picture of circuit Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

10 Experimental Setup The coil was made to fit inside a metallic box exactly. The dynode region of PMT was held at the centre of the coil by two zip ties. A hole was made in the box for the output cables of the PMT to be connected to the oscilloscope. The driving circuit was kept outside the box and the LED was attached to the inner wall facing the PMT. The coil was connected to a DC power supply. The box was closed and sealed with tape. Black insulating cloth was draped on all sides of the box and its edges were closed and stuck with tape. The experiment was performed in a dark room, and the box was thus maintained impervious to external light. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

11 Experimental Setup Figure 5: PMT inside the coil Figure 6: Completed Setup Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

12 Experimental Setup Figure 7: Completed Setup Top View Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

13 Magnetic Field vs Current in the Coil Observation of Magnetic field vs Current at the center of the coils, when bottle is inside and outside the metallic box. Stability of the coil developed is extremely important for long duration experiments. The presence of Metallic box around the coil can change the magnetic field at the center of the two coils. Tested for Hysteresis Loop and change in Magnetic Field inside the metallic box. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

14 Magnetic Field Comparison Inside/Outside Figure 8: Magnetic field vs current Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

15 Magnetic Field vs Current in the Coil Inference : The Magnetic field intensity is as planned and expected. There is negligible hysteresis in the coil Negligible changes in the magnetic field due to the metallic box Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

16 Response of the PhotoMultiplier Tube Figure 9: Schematic of PMT Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

17 Response of the PhotoMultiplier Tube The response of PMT comes out with a delay of about 1 microsecond. This might possibly be because of delay time of the circuit. We tried to make pulse width shorter, to 200 ns by increasing the frequency and keeping duty cycle same (0.001 percent). This results in complete loss of the signal.possible reason might be circuit component delays. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

18 Saturation Region of the PMT Next we plotted the number of turns in variable resistor vs the the PMT output characteristics. This is to choose a value of the current that gives a good output without saturating the PMT. Figure 10: Resistance Response of PMT Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

19 Effect of Magnetic Field on H Figure 11: Response of PMT to magnetic field Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

20 Effect of Magnetic Field on H Figure 12: Response of PMT to magnetic field Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

21 Effect of Magnetic Field on H The points are very scattered and the error in the best fit line is about This implies that the random noise due to stray light still exists. To make a correct judgement, a more robust and stray light free setup is required. Also the noise and delay due to the circuit has to be reduced. For the PMT Hamamatsu H has a factory installed magnetic shield of thickness 0.2mm. This shields it to magnetic fields. This might mean that our observations could change for a non shielded PMT. We are next going to make similar observations on a Hamamatsu PMT Model No. R7400U, and will report the findings. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

22 Measuring the effect on R7400U Figure 13: The New PMT R7400 in the Coil Setup Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

23 Effect on R7400U Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

24 Effect on R7400U Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

25 Inferences and Conclusion The PMT R7400U shows negligible effect of magnetic fields of the intensity used in the experiment. The PMT R7400U does not need to be externally shielded from magnetic fields of magnitude up to 25 mt. Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

26 Generating 100 nanosecond pulses Figure 14: Nanosecond Pulse generator Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27

27 Generating 100 nanosecond pulses Figure 15: Circuit output Nitin, Parth, Sumukh (KEK) Effect of Magnetic field on PMT 31 st May / 27