Compact HPD

In order to be utilized in such application fields as high energy physics or medical imaging, where a huge number of photodetectors are assembled in designated small area, the world's smallest HPD, the compact HPD, has been developed. The overall diameter and the length of the tube are 16 mm and 15 mm, respectively. The effective photocathode area is 8 mm in diameter. At applied voltage of -8 kV to the photocathode, the electron multiplication gain of a PD incorporated HPD (PD-HPD) is 1,600, and that of an APD (APD-HPD) is 65,000. In the pulse height distribution measurement, photoelectron peaks up to 6 photoelectrons are clearly distinguishable with the APD-HPD. Experiments established that there was no degradation of gain in magnetic fields up to 1.5 T, an important performance characteristic of the compact HPD for application in high energy physics.