Avalanche Photodiodes (APDs)
Radiation Monitoring Devices (RMD)
Avalanche Photodiodes (APDs)
Avalanche Photodiodes
Photodiodes or photo-detectors are highly sensitive semiconductor devices that use the photoelectric effect to convert light into electricity. Avalanche Photodiodes or APDs are photodetectors with an internal gain mechanism and fast rise time. Silicon Avalanche Photodiodes (Silicon APDs) are capable of achieving and sustaining higher gain than traditional APDs because they are fabricated using a deep diffused planar manufacturing process.
RMD’s compact and rugged APDs feature high quantum detection efficiency and wide spectral response. They are also insensitive to magnetic fields, unlike Photomultiplier Tubes (PMTs), which allows them to be used in hybrid PET/MRI systems. They are available in discrete devices, arrays, and position sensitive structures.
- Gain: 300-2000
- Capacitance: 0.7 pf/mm2
- Bias Voltage: 1650-1750 volts
- Quantum Efficiency at 400 nm: 50%
- Quantum Efficiency at 532 nm: 65%
- Quantum Efficiency 830 to 905 nm: 75%
- Quantum Efficiency at 1064 nm: 20%
*typical values at 22oC
- Energy Spectrum – APD Coupled with LaBr3 Crystal
Avalanche Photodiodes (APDs) find applications in LIDAR, LADAR, bio-sensors, medical imaging, telecommunications and high-energy physics.
- Gamma ray detection via scintillation crystal readout for medical and high energy physics applications.
- Direct detection of low energy X-rays with low noise, fast signals and high count rates.
- Direct detection of nuclear particles, with high efficiency even for low energy tritium betas and timing resolution capabilities down to the ten picosecond level for minimum ionizing particles
(MIPs). - High speed optical detection across the visible spectrum and beyond, including good efficiency
down to wavelengths below 200 nm (liquid Xenon scintillation) and up to neodymium YAG laser wavelength of 1064 nm.
The data collected from DragonEye Flash LIDAR (STS-127 and STS-133) experiments were instrumental to SpaceX in determining their sensor settings for the Dragon flights to ISS.