Measurements of Low-energy X-rays with a Detector Using a Plastic Scintillator and an MPPC

Abstract

An MPPC (Multi-Pixel Photon Counter) has some advantages of a low-voltage operation and easily making a multi-element type detector, when comparing with a photomultiplier tube. We tried to detect soft X-rays of less than 6 keV with a scintillation detector using an MPPC. The detector consists of a plastic scintillator (Pilot-U, 5 mm in diameter and 1 mm thick) and an MPPC (Hamamatsu Photonics, S13360-6642, 3×3 mm2, pixel size: 25 μm, without a resin window). We measured pulse-height spectra using a charge-sensitive preamplifier, cooled down to −10°C. The detector could clearly distinguish 6 keV X-rays from noise signals. We also measured time spectra of X-ray pulse structure of 2-ns intervals in the multibunch operating mode of the Photon Factory ring. A time resolution (Full width of half-maximum) of 0.51±0.06 ns was obtained at a bias voltage of +60.0 V and at −10°C, using a fast amplifier having a gain of 100.