1. PID meeting @Nagoya Univ. 31.Aug.2002 Contents 1.Introduction 2.PMT structure & Set up 3.Basic performance 4.Experiment results –Gain –Time resolution 5.Summary R&D on Fine-mesh multi-anode PMT with T.T.S.=100 ps under B  1T T.Hokuue Nagoya University, Japan Fine-mesh PMT L24 -  Multi-anode

2. PID meeting @Nagoya Univ. 31.Aug.2002 Introduction TOP counter : a new type of Cherenkov Ring Imaging detector  Single-photon sensitive with high efficiency  Position sensitive :  x  1 mm Operate under magnetic field : B = 1.5T(at Belle ) Linear-array Multi-anode Fine-mesh PMT Nucl. Instrum. Meth. : A460,326-335,2001. Hybrid Avalanche PhotoDiode (HAPD) Nucl. Instrum. Meth. : A463,220-226,2001. Transit time spread :  TTS = 100 ps Our candidates Requirements

3. PID meeting @Nagoya Univ. 31.Aug.2002 A fine-mesh PMT exhibits a good position resolution and moderate time resolution for high multiple-photons, but not for single-photon. We focused our effort to enhance the multiplication gain. Under the magnetic field :

4. PID meeting @Nagoya Univ. 31.Aug.2002 PMT structures  We made 3 different fine-mesh PMTs       Base: Multi-anode Fine-mesh PMT (R6135-L24X) made by Hamamatsu Photonics Company(HPK),Japan Common structure : - 24 anodes (readout channels) - anode size  26.5  0.8 mm - # of stages of fine-mesh dynode  24 (  ) or 19 (  ) PMT Type Distance L (mm) H.V divider network ratio Mesh Size (lines/inch),pitch -- 2.5-3 1:1:  :12000,12.5  m -- 1 2:1:  :12000,12.5  m -- 1 2:1:  :12500,9  m

5. PID meeting @Nagoya Univ. 31.Aug.2002 1.Shorter distance between photo-cathode and first dynode 2.H.V divider network ratio 3.Finer mesh size 1. Shorter distance between photo-cathode and the first dynode Transit time: E 1 : the applied voltage across L L = 2.5-3 mm  t  660 ps L = 1 mm  t  270 ps  L = 2.5-3 mm  L = 1 mm

6. PID meeting @Nagoya Univ. 31.Aug.2002 3. Finer mesh size 2. H.V divider network ratio  T.T.S.  100 ps (1: 1:  1:1)   T.T.S.  70 ps (2: 2:  1:1) (ex.) Line-forcused PMT (R5900-L16)  1:1: … :1   2:1: … :1  2000 lines/inch (12.5  m pitch)   2500 lines/inch (9  m pitch) The radius reduces with field strength. The secondary electrons would get to hit fewer dynodes Using the finer mesh would undo this reduction somewhat!!  reduced multiplication gain

7. PID meeting @Nagoya Univ. 31.Aug.2002 Set up L24 - 

8. PID meeting @Nagoya Univ. 31.Aug.2002 Basic performance Signal shape (-  ) 1. Single-photon sensitive B = 0.4 T, H.V = 2400 V The  exhibits a quite clear single- photon peak. Efficiency : 52 % (-  ) ADC distributions Rise time  1ns 63 % (-  ) 85% (-  )

9. PID meeting @Nagoya Univ. 31.Aug.2002 Basic performance 2. Position sensitive You can see clearly the field effect at weak field!! - setting 1mm-wide slit on PMT’s surface Anode-distributions(-  ) Signal spread in root-mean-square The resolution of 0.5mm is dominated by the slit width of 1mm. True resolution might be much better than this.

10. PID meeting @Nagoya Univ. 31.Aug.2002 Gain Multiplication Gain Relative gain The  : Gain  5  10 (B = 1.5T, H.V= 3400V) 6 H.V = 1600 V The  exhibits less reduction and the highest gain at 0.2T. The  : Gain  8  10 (B = 1.5 T, H.V= 2000 V) 5 Gain/Gain(B=0T)

11. PID meeting @Nagoya Univ. 31.Aug.2002 Time resolution ADC-sliced time resolution (- ,  ) & time-walk correction 0.4T,1.5kV0.6T,1.7kV1.0T,2.2kV  T.T.S  150 ps at ADC = 175-th ch at   T.T.S  100 ps at B  1T 0.4T,2.4kV  T.T.S  100 ps at ADC = 180-190 ch -- --  150 ps at B = 1.5T type 

12. PID meeting @Nagoya Univ. 31.Aug.2002 Gain vs. T.T.S. Increment of gain by factor of 10  has rather steeper relation than   improve T.T.S of 30 ps (-  ) 45 ps (-  ) The time resolution under various conditions are plotted for  and  PMTs. Both PMTs indicate that the multiplication gain of 3-5  10 are required to have a time resolution of 100ps. 7

13. PID meeting @Nagoya Univ. 31.Aug.2002 Multi-photons 2-photons   TTS  80 ps 3-photons   TTS  70 ps 4-photons   TTS  60 ps T.T.S. with Multi-photons (-  ) We already obtained high time resolution for multiple-photons.

14. PID meeting @Nagoya Univ. 31.Aug.2002 - By developing fine-mesh 24-anodes PMT Summary Time resolution : 100 ps (B  1T) 150 ps (B=1.5T) - To have a 100 ps resolution under B=1.5T  multiplication gain of 3-5  10 is required 7 - For higher gain and better T.T.S. by using finer mesh dynodes by increasingly applied H.V. on the first dynode - For Multiple-photons …  by reducing distance between the first dynode and photo-cathode