M. Bonesini - Osaka coll. meeting

1

M. Bonesini, F. Strati INFN Milano

Tests at LASA for MICE Tof PMTs

M. Bonesini - Osaka coll. meeting

2

Considerations for PMT choice

1. Rate capability (up to some MHz)2. Good timing properties (TTS)3. Sustain magnetic field ( about 100-200

gauss for TOF0, about .2 T for TOF2)

Tests at Lasa magnet test facility (end July 04, for 15 days) with Pavia MEG group to optimize choice.

Now preliminary report, more detailed report later.

M. Bonesini - Osaka coll. meeting

3

Tests done at LASA

Laser source to simulate MIP signal (about 200-300 p.e.) Laser sync out triggers VME based acquisition (TDC + QADC) 5000 events for each data point : different PMTs (fine-mesh vs mod R4998), different B-field, different inclination vs B field axis (), diff laser rate to simulate incoming particle rates

M. Bonesini - Osaka coll. meeting

4

Rate capabilities of PMTs

To have a linear signal the max ouput current must be 1/20 of the divider current (16 A for R4998, 10 A for R7761 or R5505 fine-mesh PMTs)This gives a theoretical rate capability of:

267 KHZ with R4998 167 KHZ with R7761,R5505BUT !!! Divider can be modified only for

R4998 (going up to 1.67 MHZ)

M. Bonesini - Osaka coll. meeting

5

Test magnet at LASA (B up to 1.2T)

PMT under test

M. Bonesini - Osaka coll. meeting

6

Used laser light sourceLight source: Hamamatsu fast laser ( 405 nm, FWHM 60 ps, 250 mW peak power) PLP-10Optical system: x,y,z flexure movement to inject light into a CERAM/OPTEC multimode fiber (spread 14 ps/m) PMT under test

Laser light Signal ~ 200 p.e.to reproduce a MIP as

measured with a powermeter

M. Bonesini - Osaka coll. meeting

7

Fine-mesh phototube Properties

Under test: 1” (R5005), 1.5” (R7761), 2” (R5946).Results for G,TTS, rate efects in B-fields availablesoon

M. Bonesini - Osaka coll. meeting

8

PMT rate studies R4998 with modified

divider circuit: booste for last dynodes

Lab rate tests done with mod R4998,

R7761 and R5946 in/outB-field

Nominal: up to 1.5 MHz

R 4998 R 5505 Structure Linear Focused Fine Mesh

Stages 10 15 Gain 5.7 106 5 105 B=0

1.8 104 B=1 T Rise Time 0.7 ns 1.5 ns

Transit Time 10 ns 5.6 ns Transit Time

Jitter 0.16 ns 0.35 ns

M. Bonesini - Osaka coll. meeting

9

R4998 with modified divider (booster for last dynodes) + mu-metal

shielding

One specimen on loan in June 2004 for tests

M. Bonesini - Osaka coll. meeting

10

Gain in magnetic field for R4998

M. Bonesini - Osaka coll. meeting

11

Timimg properties of R4998

M. Bonesini - Osaka coll. meeting

12

Rate effects studies for R4998

• done with available R4998 with modified divider from Hamamatsu (booster on last dynodes) on loan

•Light signal corresponds to ~ 200 p.e.

M. Bonesini - Osaka coll. meeting

13

Conclusions

Only some results on R4998 mod have been shown (we finished data taking for tests last Friday)A lot of results on fine-mesh PMTs (1”, 1.5”, 2”) have been obtainedAll will be shown later