The Canberra Model 2016 Amplifier/TCA is a single-wide NIM module designed for signal processing in x-ray detectors, particularly in high-rate applications such as Extended X-ray Absorption Fine Structure (EXAFS). It integrates an amplifier, a triple channel analyzer (TCA), and a multiplexer function, offering a compact solution for large-scale systems.
Function Description
The Amplifier section provides essential signal processing, including gain, filtering, baseline restoration, and ICR pulse discrimination. It is based on the Canberra Model 2025-2026 series amplifiers, known for their use in x-ray and gamma-ray spectroscopy. The 2016A model offers higher throughput rates with shaping times of 1/8, 1/4, 1/2, 1, 2, and 3 µs, while the 2016B model provides longer time constants (1/4, 1/2, 1, 2, 4, and 6 µs) for high resolution at lower rates and for low energy (<1 keV) applications.
The Triple Channel Analyzer (TCA) comprises three independently computer-controlled single-channel analyzers. Each SCA generates a logic pulse output for input pulses falling within its preset energy window. Window settings are configured via computer control through an Ethernet link to an Acquisition Interface Module (AIM) and Canberra's Instrument Control Bus (ICB). For convenience, windows are set symmetrically around a centroid voltage (energy) level. An optional pileup rejector, when enabled, inhibits SCA outputs for signals distorted by pile-up.
The Multiplexer Function facilitates signal routing for setting up each SCA window and normalizing signal levels (gain) using a multichannel analyzer (MCA). "SELECTED AMP" outputs are typically daisy-chained to an ADC signal input, and "SELECTED SCA" outputs to the ADC GATE input. This allows the MCA to accumulate or exclude events based on the selected SCA window.
ICB Control manages SCA settings and multiplexed output selections. A single AIM acts as a master, addressing up to 16 slave devices. Larger systems can be implemented by adding more AIMs. Software control for the 2016 and other ICB NIM modules is available through Canberra's Genie-2000/Genie-PC and Genie-VMS software packages, allowing control over SCA centroid windows, SCA Polarity Invert, automatic or manual ICR Threshold, SCA select, and PUR enable. The software also verifies the instrument's serial and model numbers.
Important Technical Specifications
Inputs:
- INPUT: Accepts positive or negative tail pulses from an associated preamplifier. Amplitude up to 10 V (divided by selected gain), 25 V maximum. Rise time is less than shaping time constant. Decay time constant ranges from 40 µs to ∞. Polarity is set by internal jumpers. Input impedance (Zin) is 2 kΩ to >0.5 kΩ, depending on input polarity and coarse gain. Front and rear panel BNC connectors.
- INHIBIT: Accepts a standard TTL logic signal from an associated reset preamplifier to inhibit SCAs and reset the pileup rejector during preamp reset cycles. Positive or negative true signal polarities are selectable via internal jumper. Loading is 4 kΩ resistor connected to +5 V for positive true or ground for negative true. Rear panel BNC.
Outputs:
- AMP OUT: Provides positive, linear, actively filtered shaped unipolar pulses. Amplitude linear to +10 V, 12 V max. DC restored to 0.5 mV (factory calibrated). Output impedance (Zout) is <1 Ω or 93 Ω (internally selectable). Short circuit protected. Front panel BNC.
- SELECTED AMP: Provides positive computer-selected, linear, actively filtered shaped unipolar pulses. Amplitude linear to +10 V, 12 V max. DC restored to 0.5 mV (factory calibrated). Zout is 93 Ω. Short circuit protected. Front panel BNC.
- SELECTED SCA: Provides a standard positive TTL logic output signal coincident with computer's selection of SCA one, two, or three. Pulse width is 0.1 µs nominal. Rise and fall times are <25 ns. Zout is 51 Ω. 6mA drive capability for TTL high or low level. Front panel BNC.
- ICR: Provides a standard positive TTL logic signal corresponding to input count rate. Disabled by INHIBIT. Positive true. Width nominally 150 ns. TTL with 1 kΩ pull-up resistor through 47 Ω output resistor. Rear panel BNC.
- SCA 1, 2, or 3 (Fast NIM Option): Provides negative current output -16 mA into 50 Ω. Rise time <5 ns. Pulse width <0.1 s. Rear panel EPL00-250NTN LEMO connector.
- SCA 1, 2, or 3 (TTL Option): Provides positive logic +5 V nominal pulse level. Pulse width <0.1 µs. Rise and fall times <25 ns. Rear panel EPL00-250NTN LEMO connector.
- SCA 1, 2, or 3 (50 Ω TTL Option): Provides positive logic +5 V nominal pulse amplitude. Zout is 50 Ω. Pulse width <0.1 µs. Rise and fall times <25 ns. Rear panel EPL00-250NTN LEMO connector.
Indicators:
- ICB READY: Green LED. Steadily on indicates TCA parameters are loaded and active; blinking indicates selected SCA is active.
- ICR RATE: Multicolor LED. Red indicates PUR is on; Green indicates PUR is off. Intensity is count rate dependent.
Pileup Rejector:
- Pulse Pair Resolution: 250 ns.
- Minimum Detectable Signal: Limited by detector/preamp noise characteristics.
- PUR Threshold: Auto or Manual Adjust mode; computer selectable.
- PUR Enable: On or Off; computer selectable.
Performance:
- Gain Range: Continuously variable from x2.5 to x1500.
- Temperature Stability: AMP OUT Gain: 0.005%/°C, dc level: 7.5 V/°C.
- Integral Nonlinearity: 0.04% over total output range for 2 µs shaping.
- Overload Recovery: AMP OUT output recovers to within 2% of full scale output from x1000 overload in 2.5 non-overloaded pulse widths at full gain, at any shaping time constant, and with P/Z properly set.
- Pulse Shaping: Near-Gaussian or near-triangular shape; one differentiator; three active filter integrators realizing eight-pole shaping network.
- Restorer: Active gated.
- SCA Nonlinearity: <0.25% of full scale.
- SCA Stability: <±0.005%/°C (50 ppm/°C) of full scale.
- SCA Range: 1000:1.
- SCA Pulse Pair Resolution: <250 ns using 0.125 µs shaping.
Power Requirements:
- +24V dc - 100 mA
- +12 V dc - 175 mA
- +6 V dc - 350 mA
- -24 V dc - 120 mA
- -12 V dc - 130 mA
- -6 V dc - 200 mA
Physical:
- Size: Standard single-width NIM module 3.43 x 22.12 cm (1.35 x 8.71 in.) per DOE/ER-00457T.
- Net Weight: 1.5 kg (3.3 lb).
- Shipping Weight: 2 kg (4.4 lb).
Environmental:
- Operating Temperature Range: 0 to 50 °C.
- Humidity: Up to 95% non-condensing.
- Tested to EN 61010, Installation Category I, Pollution Degree 2.
Usage Features
Front Panel Controls:
- COARSE GAIN: Selects one of eight coarse gain factors (x5 to x1000).
- FINE GAIN: Selects variable gain factor (x0.5 to x1.5) by which COARSE GAIN is multiplied. Ten-turn locking dial precision potentiometer with 0.03% resettability.
- SFG (Super Fine Gain): Multi-turn screwdriver potentiometer adjusts fine gain with resolution better than 0.0063%.
- SHAPING TIME: Selects one of six shaping time constants (2016A: 1/8, 1/4, 1/2, 1, 2, 3 µs; 2016B: 1/4, 1/2, 1, 2, 4, 6 µs).
- P/Z (Pole/Zero): Multi-turn screwdriver adjustable potentiometer to optimize amplifier baseline recovery and overload performance. Range: 40 µs to ∞.
- SHAPING MODE: Selects triangular or semi-Gaussian pulse shaping for the unipolar output.
- ICR THRESH: Multi-turn screwdriver potentiometer adjusts Fast Discriminator reference level for manual PUR threshold mode.
- SELECTED SCA: Provides a positive true TTL-logic signal from the selected SCA.
- SELECTED AMP: Provides prompt positive, linear, unipolar pulses from the selected 2016.
- AMP IN: Accepts positive or negative tail pulses from an associated preamp.
Internal Jumpers:
- RESTORER MODE: Two-position jumper selects symmetrical or asymmetrical baseline restorer modes (factory set to symmetrical).
- POLARITY: Two 2-position jumpers must be set identically to select input polarity (factory set to negative).
- INHIBIT POLARITY: Two-position jumper selects INHIBIT input polarity (positive or negative true; factory set to positive).
- AMP OUT IMPEDANCE: Two-position jumper selects Zout <1 Ω or 93 Ω (factory set to <1 Ω).
Computer Controls:
- SCA Window centroid and width.
- PUR enable/disable.
- TCA enable/disable and polarity.
- PUR threshold auto/manual.
Calibration and Normalization:
The device supports calibration and gain normalization using Genie-VMS or Genie-PC/Genie-2000 software. This ensures amplifier gain and SCA windows are set to read directly in energy (keV) and that MCA energy calibration corresponds to the SCA. The process involves adjusting amplifier gain until peaks of interest are displayed in the SCA windows, setting SCA window parameters, and then normalizing gains across multiple channels.
Pole/Zero Matching:
Crucial for maintaining good resolution and low peak shift at high count rates. It involves adjusting the P/Z control to ensure the unipolar pulse returns cleanly to the baseline without overshoots or undershoots. For reset preamplifiers, P/Z compensation is not required, and the control should be set fully counterclockwise (infinity).
Triangular Shaping:
Offers improved signal-to-noise ratio (SNR) and reduced electronic noise, making it less sensitive to detector ballistic deficit. This can improve resolution but at the expense of reduced maximum throughput due to longer signal processing time.
ICR Threshold Adjustment:
The ICR threshold can be set manually or automatically. For optimum PUR performance, it should be set just above the system noise level.
Optimizing the Discriminator:
This procedure ensures the discriminator sensitivity is at its lowest setting, just above the noise level, by adjusting the ICR THRESH control.
ADC Peak Detect Adjustment:
The ADC's Delayed Peak Detect feature simplifies SCA calibration. The Delayed Peak period should be adjusted to include the SCA signal but not extend beyond it, minimizing artifacts at high count rates.
Maintenance Features
Cleaning:
The front panel can be cleaned with a soft cloth dampened with warm water after removing power. Liquids should not be used on the NIM wrap, side, or rear panels due to access holes.
Preventive Maintenance:
No specific preventive maintenance is required for this unit.
Installation Considerations:
The module is designed to operate in a standard NIM Bin and Power Supply. Proper air circulation is important, especially when rack-mounted with other heat-generating equipment. Compliance with European Union requirements is ensured, provided the unit is installed in a CE compliant NIM Bin and Power Supply, with proper grounding, single-point external cable access, and blank panels covering open bin areas. Repairs should be performed by qualified Canberra service representatives to maintain compliance and warranty.
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