Design and feasibility of active matrix flat panel detector using avalanche amorphous selenium for protein crystallography

Abstract

Protein crystallography is the most important technique for resolving the three-dimensional atomic structure of protein by measuring the intensity of its x-ray diffraction pattern. This work proposes a large area flat panel detector for protein crystallography based on direct conversion x-ray detection technique using avalanche amorphous selenium (a-Se) as the high gain photoconductor, and active matrix readout using amorphous silicon (a-Si:H) thin film transistors. The detector employs avalanche multiplication phenomenon of a-Se to make the detector sensitive to each incident x ray. The advantages of the proposed detector over the existing imaging plate and charge coupled device detectors are large area, high dynamic range coupled to single x-ray detection capability, fast readout, high spatial resolution, and inexpensive manufacturing process. The optimal detector design parameters (such as detector size, pixel size, and thickness of a-Se layer), and operating parameters (such as electric field across the a-Se layer) are determined based on the requirements for protein crystallography application. The performance of the detector is evaluated in terms of readout time (<1 s), dynamic range (approximately 10(5)), and sensitivity (approximately 1 x-ray photon), thus validating the detector's efficacy for protein crystallography.

Amorphous and Polycrystalline Photoconductors for Direct Conversion Flat Panel X-Ray Image Sensors

“…A further often overlooked advantage of avalanche multiplication is to increase the dynamic range of a system by permitting the maximum signal capacity to be adjusted by changing the effective multiplication gain. There have been a number of recent studies by Rowlands and coworkers that have examined the use of avalanche in a-Se for medical imaging applications [132–137] as well as in protein crystallography [138,139]. These imaging applications use both indirect and direct x-ray detection techniques and then avalanche, or carrier multiplication, in a-Se to achieve gain.…”

Novel silicon x-ray detector with TFT readout

“…Once the readout is evacuated, V BK bias returns to positive to confine photogenerated charges from incoming X-ray photons. The integration period can be kept as short as possible since the readout scheme is rather based on active pixel sensor (APS) readout than passive pixel readout which was accepted as a standard readout scheme for amorphous selenium detectors [3]. Figure 6.…”

“…However, spatial resolution and a complex fabrication process are two major hurdles that prevent SDDs from seeing widespread use in diffraction imaging and protein crystallography. To overcome the issues with SDDs, we proposed a new type of silicon radiation detector integrated with a hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) readout technology intended for low X-ray energy detection with high spatial resolution [3]. This work aims to extend our previous effort by examining in detail the operation of the proposed integrated silicon TFT detector and to evaluate its X-ray sensitive performance via numerical analysis.…”

PVDF Sensor Stimulated by Infrared Radiation for Temperature Monitoring in Microfluidic Devices

“…Moreover, a thermal model based on the analysis of heat transfer mechanism is developed for the characterization of the transducer. The pyroelectric contact thermometer is composed of a thin film of PVDF coupled with a microfluidic device and includes an infrared (IR) light source and a charge amplifier that generates a suitable voltage signal in response to the electrical charge [20,23,24,25]. As a consequence of the modified design of the transducer, the use of mechanical components (such as shutters) and adjunctive reference sensor (e.g., thermocouple) are eliminated in the proposed configuration.…”