Phototube Test for MiniPlug Calorimeter

  This page describes the status of the test of MAPMT's to be used for the MiniPlug calorimeter. We are planing to use 16-channel MAPMT's manufactured by Hamamatsu ( H6568-10/R5900 M16). Two types of MAPMTs are provided by the manufacturer: one with a 2 mm thick window and a 4 MOhm voltage divider (H6568-16 MOD), and another with a 1mm thick window and 1 MOhm voltage divider (H6568-16 REV). The characteristics of H6568-10/R5900 M16 MAPMT's specified for the MiniPlug calorimeter are shown in here.

Photograph of a MAPMT used for the MiniPlug calorimeter

  Since individual PMT's may have substantially different characteristics from those provided by the manufacturer, it is important to measure all the PMT's we receive and verify that they conform to our requirements. We have a setup which allows us to evaluate MAPMT's. The setup which we used is shown in this figure. You can find more details in this document.

Note 1), The High Voltages values shown in the above table are the HV values at which that PMT shows approximately the same output as the other PMT's.
Note 2), Figures in the "Relative Gain" column show (top) relative gains of 16 MAPMT channels, (middle) differences between our measurements and numbers from Hamamatsu, (bottom left) relative gains of 6 grouped channels. ( Channel-A : Channel-1,2,3,    Channel-B : Channel-5,6,7,    Channel-C : Channel-9,10,11,    Channel-D : Channel-13,14,15,    Channel-E : Channel-16) and (bottom right) differences between relative gains of 6 grouped channels and expectations from measurements of 16 individual channels.
Note 3), The uniformity is defined as the ratio of the minimum to the maximum relative gains. Distributions for the uniformity are shown here.

• Ratio of the sum of 16 MAPMT channels to the output from the last dynode

We will use signals from the last dynode output as a miniplug trigger. Also, they will initially be used as the only readout channels from the miniplug calorimeter. So, it would be important to compare the response of the last dynode to the sum of the sixteen individual channels.

• Accuracy of the measurement of relative gains

The setup which we used has 16 readout channels. We studied the channel-dependence of the signal by rotating MAPMT's by 90^o, 180^o and 270^o, and comparing signals from the same anode of the MAPMT but measured at the different channel. The results are shown here. The differences are 6 % at most.
• Stability of our setup

We studied the stability of our setup by repeating measurements in a certain period. During that period, both the high voltage supply and the pulse generator for the LED were kept on. The results are shown in here. The measured ADC counts went down about 3 % in the first 20 minutes, and after that, they got very stable. In the meanwhile, since the ADC counts for all the PMT anodes went down in a similar manner, relative gains were very stable all the time (within 1 %).
• Data reproducibility

We studied the data reprodicibility in our setup by repeating measurements with (1) turning on/off the pulse generator for the LED, (2) turning on/off the high voltage supply for the PMT, and (3) re-mounting the PMT before each measurement. Results are shown in (1), (2), and (3). The variation in ADC counts is less than 1 % in the case of (1) and (2), and about 1-2 % in the case of (3). The variation in relative gains is less than 1 % in all the cases.
• Channel mapping for the MiniPlug MAPMT

We are planing to group outputs from three channels into one channel to reduce the cost for the readout electronics. The scheme for this grouping is shown here.

Links

• The CDF Forward Detector Project Page
• MiniPlug Carolimeter
• Photomultiplier Tubes for the Forward Detectors
• Cosmic-ray Test of MiniPlug Calorimeter