DAQ system

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This is an image map. Click on a section of the picture to go to the page for that item.

VME CratesVME CratesVME CratesCollector BoxCollector BoxCollector BoxDAQ Power SupplyDAQ Power SupplyDAQ Power SupplyDAQ Power SupplyLiquid NitrogenLiquid NitrogenGammasphere frame (without detectors in it)
Figure 1. DAQ System circled in red; one rack for each of the four "hemispheres" of Gammasphere

Gammasphere's DAQ system (data acquisition system) is now placed on relay racks by each side of its "hemispheres". Each of the racks for the DAQ consists of a power supply, a collector box, and a VME crate. The data acquisition system observes, interprets, and modifies data taken from Gammasphere and appropriately presents it to the user.

The picture above provides an overall map to the naming conventions associated with the system. Cardinal directions are shown in purple text, process variable (EPICS) names are shown in green text and network IDs are shown in red text. There are multiple computers within the DAQ system:

These devices are used both by data acquisition and by control & monitoring
Network name IP address Description
ioc01: 192.168.203.141 MVME5500 VME processor used for control and readout
ioc02: 192.168.203.142 MVME5500 VME processor used for control and readout
ioc03: 192.168.203.143 MVME5500 VME processor used for control and readout
ioc04: 192.168.203.144 MVME5500 VME processor used for control and readout
ioc05: 192.168.203.145 MVME5500 VME processor used for control and readout
ioc06: 192.168.203.177 MVME5500 VME processor used for control and readout
ioc07: 192.168.203.178 MVME5500 VME processor used for control and readout
ioc08: 192.168.203.179 MVME5500 VME processor used for control and readout
ioc09: 192.168.203.180 MVME5500 VME processor used for control and readout
ioc10: 192.168.203.183 MVME5500 VME processor used for control and readout
ioc11: 192.168.203.181 MVME5500 VME processor used for control and readout
ioc12: 192.168.203.182 MVME5500 VME processor used for control and readout
These devices are used by control & monitoring only.
Network name IP address Description
gs-cne 192.168.203.88 Raspberry Pi inside the North East Collector box
gs-cnw 192.168.203.149 Raspberry Pi inside the North West Collector box
gs-cse 192.168.203.42 Raspberry Pi inside the South East Collector box
gs-csw 192.168.203.26 Raspberry Pi inside the South West Collector box
These devices are used by directly logging into them to control power to the VME crates, network switches and terminal servers.
Network name IP address Description
gs-pdu-north 192.168.203.224 Power Distribution Unit for the North Hemisphere
gs-pdu_south 192.168.203.225 Power Distribution Unit for the North Hemisphere
These devices are used by directly logging into them to connect to the console ports of IOC01 through IOC12.
Network name IP address Description
gs-ts-north 192.168.203.91 Terminal server providing console port access for ioc07 through ioc12
gs-ts_south 192.168.203.186 Terminal server providing console port access for ioc01 through ioc06
These devices are associated with the liquid nitrogen subsystem.
Network name IP address Description
lnfill 192.168.203.121 Embedded VME processor that hosts the EPICS databases for valve status and valve control
ln2con 192.168.203.148 Linux computer that lnfill boots from

When Gammasphere collects data, single-ended signals are first collected from the slope box for the Ge Center, Ge Sides, and BGO segment. The signals are converted to differential signals by the SBX, and are then sent to the collector box so the signals can properly be routed to the digitizers. The digitizers process and output the desired information to the user based upon their data specifications. The DAQ system is an FPGA-based design that provides communication hub interfacing the preamp, power board, dongle and slope box to EPICS through serial interface. Analog signal paths are completely software controlled.

DAQ System Function

The Gammasphere DAQ system consists of VME crates, IOC Modules, Digitizers and Trigger Modules. The original "analog" implementation of Gammasphere using the VXI modules used a charge-integrating ADC methodology and did not continuously digitize the data from the detectors. The Digital Gammasphere system (2010s) introduced the digitizers as a replacement for the charge-integrating ADC functions of the VXI modules and replaces the "analog" system's trigger by a new trigger system, requiring a redesign of the DAQ. The later "Gammasphere Upgrade" project (2019-2023) that resulted in the SBX, preamp and collector box hardware did not materially affect the DAQ but replaced all of the remaining control, monitoring and power distribution functions of the VXI system allowing removal of the VXI system and associated cable plant.

Each digitizer in the system consists of 10 channels, but should be conceptualized as a pair of two sub-digitizers consisting of five channels each. There are two types of digitizers: master and slave. A pair of channels in a master digitizer receives signals from the Ge center and BGO sum from a single Gammasphere detector, while a channel-pair in the slave digitizer receives signals from the Ge side and BGO pattern. All channels in all digitizers run continuously.

There are two types of Digitizers (Master and Slave) and well as Trigger (Master and Router). All channels in all digitizers run continuously. There are two types of digitizers (master and slave) as well as two types of triggers (master and router).

When discriminator logic within the digitizer firmware marks edges of gamma-ray signals, energy sums, timing and other data are stored in a header identifying the event. If the event is selected for readout by the trigger system, the header and a programmable amount of waveform is transferred from the channel to the board-wide FIFO (first in, first out) data holder. Similarly the trigger modules have FIFO buffers that store information each time a trigger acceptance message is issued to the digitizers. The IOC scans the FIFOs of all modules to see if there is data to read out through a series of programs named inLoop, outLoop and MiniSender. If data is available, the inLoop program reads it and stores the data read into memory buffers. Program outLoop verifies the integrity of the buffers and then hands control of the buffers to the MiniSender program. A separate program running on a different computer called “gtReceiver” sends messages to each IOC's MiniSender program when it is capable of receiving data. The MiniSender program of each IOC, in response to requests from gtReceiver, then breaks apart buffers into UDP packets and sends them to gtReceiver. The gtReceiver program then stores the data received to files that may be organized by digitizer or by channel.

Gammasphere DetectorsGammasphere DetectorsGammasphere DetectorsThe Slope BoxThe Slope BoxThe Slope BoxThe Slope Box ExtensionThe Slope Box ExtensionThe Slope Box Extension
Figure 2. Diagram of the DAQ system process.


To view how this system is controlled, go to DGS Commander EDM Screens.

Go back to Digital Gammasphere Upgrade Project