The Link 2020 is not a standalone pulse processor; rather, it is a set of circuit boards that are a subsystem of a larger EDS system. The example described here is for the 2020 that is a subsystem of the Link AN10000 system.
The 2020 for the AN10000 is a set of 3 circuit boards. The top board is digital circuitry, the middle board is the Analog-to-Digital Converter (ADC), and the bottom board is the pulse processor. Sometimes these three together are referred to as the 2020; other times, just the bottom pulse processor board is referred to as the 2020. The pulse processor output (a negative-going step pulse) exits via a LEMO connector and is injected to the ADC via SK3.
The 2020 is a "step" pulse processor, so the interface with the 4pi system is made through only a few connections. The 4pi Spectral Engine replaces the middle (ADC) board of the 2020, and and additional inputs from the pulse processor board are required if correct dead-time information is needed. The top digital board is not relevant to the 4pi interface. The modifications described here will create the following connection schematic:
Option 1: The high-profile SIU has a jumper that allows simple inversion of the negative step pulse. Connect the pulse processor LEMO output directly to the PHA Input cable that is connected to the PHA Input BNC connector on the rear panel of the SIU. Then, move the jumper-clip on the SIU internal Jumper 7 (JMP7) from pins 1-2 to pins 2-3.
Option 2: The low-profile SIU has no mechanism for inverting the negative step pulse, and you must connect to the 2020 circuit board at a point where the signal is not inverted. The best location for this is on the ADC board; therefore, the connector from the LEMO to SK3 ahould be left in place. The patch to the ADC board is shown below. We recommend that the connection be made with 50-ohm coaxial cable with the sheath tied to the local ADC ground.
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IC6 is an inverting amplifier, and its output connects to a couple of links on the circuit board that may or may not be closed. A connection should be made to the output of IC6. It is up to the user to determine the most appropriate place to make the connection. |
The remaining two connections (green) at the 2020 are the Rate Meter (fast channel) and the Live-time Correction. Both of these connections may already be brought out to a BNC patch panel near the 2020. If not, the connection again needs to be made to the board directly, as shown below:
In general, the connections from a 3rd party pulse processor to the SEII are typically made through the external Scanning Interface Unit's DB-25 rear-panel connector labelled PHA Logic I/O. However, in certain circumstances, a direct connection to the DB-37 connector on the back of a SEII board is allowed. If a connection is made directly to the SEII board, Option 2 above must be selected. Shown below are the pin-out connections.
SEII DB37 SIU DB25 2020
(ADC Busy) 4/22 --->> 2/15 --->> no connection
(Pulse Reject) 5/23 <<--- 3/16 <<--- no connection
(Live Time) 3/21 <<--- 4/17 <<--- Live-time Correction (green)
(Fast Channel) 2/20 <<--- 6/19 <<--- Rate Meter (green)
(PHA Input) 6/24 <<--- BNC <<--- Output Option 1 or Option 2
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