Stanford Research SR400 Dual-Channel Gated Photon Counter

The Stanford Research Systems SR400 Dual-Channel Gated Photon Counter integrates amplification, discrimination, gate generation, and counting into a single microprocessor-controlled instrument for high-precision, low-light-level measurements. It eliminates the need for complex modular setups in time-resolved detection applications.

– Technical Specifications

Counting Performance
• Two independent counting channels, each capable of 200 MHz count rates
• Three fast counters (A, B, T) operating up to 200 MHz
• Pulse-pair resolution: 5 ns
• Three counting modes: fixed time duration, fixed count threshold, or fixed trigger count
• Programmable scan cycles from 1 to 2000 count periods per scan
• Configurable dwell time: 2 ms to 60 s between consecutive count periods

Gating and Timing
• Gate widths: 5 ns to 1 second
• Gate delay: 25 ns to 1 second from external trigger
• Fixed or scanned gate positioning modes
• Independent discriminators for each channel with selectable threshold: −300 mV to +300 mV (0.2 mV steps)
• Discriminator output: NIM-level pulses (−0.7 V)
• Detects pulses of either polarity

Signal Inputs
• Two analog signal inputs (A and B), internally terminated to 50 Ω
• Input voltage range: ±300 mV
• Input protection to ±5 VDC
• Amplifier bandwidth: DC to 300 MHz
• Minimum detectable pulse: 10 mV

Processing Capabilities
• Background subtraction, synchronous detection, source compensation, and pile-up correction
• Gate scanning for time-resolved measurements and waveform recovery
• 10 MHz crystal timebase and external trigger input sources

– Key Features

Microprocessor control streamlines operation across multiple integrated functions. Independent channel architecture enables simultaneous dual-channel measurements. Variable gate delays and widths support both fixed-window and time-scanned counting protocols. Precise threshold control and pulse polarity detection accommodate diverse signal sources.

– Typical Applications

Fluorescence lifetime measurements, time-resolved spectroscopy, quantum optics experiments, and photon-counting applications requiring nanosecond-scale timing resolution.

– Compatibility & Integration

Preamplifier compatible. NIM-level discriminator outputs facilitate integration with external timing and control systems.