A new spectroscopic imager for X-rays from 0.5 keV to 150 keV combining a pnCCD and a columnar CsI(Tl) scintillator

Abstract

By combining a low noise fully depleted pnCCD detector with a columnar CsI(Tl) scintillator an energy dispersive spatial resolving detector can be realized with a high quantum efficiency in the range from below 0.5 keV to above 150 keV. The used scintillator system increases the pulse height of gamma-rays converted in the CsI(Tl), due to focusing properties of the columnar scintillator structure by reducing the event size in indirect detection mode (conversion in the scintillator). In case of direct detection (conversion in the silicon of the pnCCD) the relative energy resolution is 0.7% at 122 keV (FWHM = 850 eV) and the spatial resolution is less than 75 μm. In case of indirect detection the relative energy resolution, integrated over all event sizes is about 9% at 122 keV with an expected spatial precision of below 75 μm.

Applications of a pnCCD detector coupled to columnar structure CsI(Tl) scintillator system in ultra high energy X-ray Laue diffraction

“…Comparing the two detection processes of pnCCD and CsI(Tl) we can conclude that (a) 273 signal electrons per keV photon energy deposited in the silicon of the pnCCD are delivered while (b) we get 51 (experimental value in this work is 47) electrons per keV from the CsI signal, at the same incident energy. The direct conversion in the Silicon leads to a 5.4 (experimental value in this work is 5.8) times higher output signal compared to the indirect signal from the CsI [3]. But the very important difference between the two detection schemes for our application in crystallography is the 50% quantum efficiency at 100 keV of the CsI(Tl) compared to less than 1% for silicon.…”

“…A novel X-ray imaging system has been developed recently by PNSensor GmbH in Munich. It is based on a combination of a micro-columnar Thallium doped Cesium Iodide (CsI(Tl)) scintillator with a silicon pnCCD detector [3]. CsI scintillators doped with Thallium (Tl) has a high stopping power for γ-rays compared to Si and Ge due to its high mass density of 4.5 g/cm 3 and high atomic number of Z Cs = 55 -1 - and Z I = 53.…”

“…It is based on a combination of a micro-columnar Thallium doped Cesium Iodide (CsI(Tl)) scintillator with a silicon pnCCD detector [3]. CsI scintillators doped with Thallium (Tl) has a high stopping power for γ-rays compared to Si and Ge due to its high mass density of 4.5 g/cm 3 and high atomic number of Z Cs = 55 -1 - and Z I = 53. It has a high light yield of about 60 photons/keV [4] and its emission spectrum is in the visible range with a peak maximum located at about 550 nm [5].…”

“…In our synchrotron experiments we used a test pnCCD with 128×128 pixels operated in a frame store three-phase transfer mode. Structure -2 - and function of the system were tested by radioactive sources and the results are discussed in details in [3]. In the present paper we focus on applications in X-ray crystallography using white synchrotron radiation.…”

High-spatial-resolution X-ray Imaging by Scintillator in Silicon Collimator

“…When CsI is separated by columnar crystals and light having an angle that does not satisfy the total reflection condition is incident on the boundary, the light is transmitted to the adjacent columnar crystal. (17) The light does not affect adjacent pixels in the collimator because the silicon does not permit the transmission of visible light. The absorption of visible light by silicon does not affect the MTF because the MTF does not depend on the light intensity.…”