T3B Software Development

Having the T3B layer assembled, the T3B cells powered and connected to the Picoscopes, one needs to configure the oscilloscopes, operate them in a test beam optimized way and control and validate the recorded data. A new data acquisition software and an online monitor suiting the requirements for a successful T3B operation have been designed and developed from scratch.

Data Acquisition Software

Unlike the data acquisition software (DAQ) provided by Picotech [73], the T3B DAQ can control multiple Picoscopes at the same time, it provides a repetitive acquisition loop that can be started and interrupted by an external trigger source and it can switch dynamically between predefined sets of oscilloscope configuration settings. The T3B DAQ is a C++ based, object oriented framework built around the oscilloscope driver delivered by the manufacturer and accessed by the user via a graphical user interface based on Qt [76]. A picture of the main window of the T3B DAQ is shown in Figure 4.8. It is subdivided into a section for run steering that can be handled by every member of the crew working at the test beam, a section that is meant to be only modified by T3B experts and a section that notifies the user of the progress of the run. In the steering section the user can select a set of preconfigured oscilloscopes settings and start and stop the acquisition loop by clicking the corresponding button. In the expert section the user can enforce an interruption of the acquisition in case of an error and modify the run number and the location the data is saved to. Here, the user can furthermore switch to the configuration window (not shown) which allows a modification of the oscilloscope settings such as the vertical range, the time base, the trigger option and more. The notification section indicates the current status of the five PS6403, the PS2203 oscilloscope and the DAQ and displays additional information on the data acquired so far, the disk space used and the duration of the ongoing run. Under run notes the user can document any kind of information related to the run he is acquiring. The underlying workflow of the DAQ software under test beam conditions, hidden underneath the graphical interface, is shown in Figure 4.9. After the start-up of the DAQ and the connected oscilloscopes, the control is passed to the user who needs to configure or just select the settings suitable for the next run and eventually start the data taking. Then the DAQ software enters the fully automated acquisition loop. The settings are uploaded to the oscilloscopes and the DAQ waits for the particle spill to arrive in the following. During this time, the PS2203 is in capturing mode and notifies the DAQ of the spill start, meaning that it detected the rising edge of the spill signal delivered by the accelerator. When this happens, the capturing mode (rapid block) of the PS6403 is activated and the five oscilloscopes are triggered synchronously by an external source indicating the arrival of individual spill particles (see Section 4.3 for details on the trigger setup specific for the different test beam phases). When the PS2203 detects the end of the spill the rapid block mode of the PS6403 is interrupted

Figure 4.8: Picture of the main window of the data acquisition software.

and they transfer the acquired data to the DAQ PC. Afterwards the settings of the so-called intermediate run mode (IRM) are uploaded to the PS6403. This mode is usually used to record random thermal darkrate from the SiPMs. It allows for a live determination of the SiPM gain which is crucial for the calibration procedure of the T3B data (see Chapter 5). In the IRM the PS6403 capture a predefined number of events in self triggered mode provided this does not take longer than a specified maximum time

Tmax. Otherwise the capturing will be interrupted. When the IRM data is transferred

to the DAQ PC, the physics mode settings are uploaded to the oscilloscopes and the whole acquisition sequence starts over. The run can be ended at any time by the user, but this does not cause the DAQ to interrupt the sequence, but it waits till the physics and the intermediate run mode are finished and drops out of the sequence in a controlled way then. For a successful test beam operation the DAQ sequence and the settings needed to be optimized in terms of speed and timing so that the oscilloscopes finish all activity before the arrival of the next spill. The remaining limiting factor is the data transfer speed achievable with the USB 2.0 standard. It restricts the amount of events that can be captured per spill and that the T3B experiment can process on time. More details on the data acquisition software can be found in [77].

Start DAQ Start Oscilloscopes User: Configure Oscilloscopes Run Start Physics Mode: Load Osci Configuration

Wait for Spill Start

Spill Start

Switch to Capturing Mode Capture Waveforms

Spill End

PS2000

PS2000

Interrupt Capturing Mode Transfer Data to PC

and Store

Intermediate Mode: Load Osci Configuration

Capture N Waveforms within T max Transfer Data to PC and Store Run Stop Stop DAQ

Start Capturing Mode

Restart Capturing Mode

Notify

Notify

Figure 4.9: Workflow of the data acquisition software under test beam conditions. After the initialisation and configuration of the oscilloscopes (top), the acquisition loop can be started. The physics run mode recording the particle events (blue for the PS6403, black for the spill triggering of the PS2203) is alternated by the intermediate run mode recording a set of calibration events (green) until the user stops the acquisition (bottom).

Online Monitor

A C++ based online monitor (OM) using the data analysis framework ROOT [78] has been designed as a complement to the T3B DAQ software. The OM allows the user to verify the successful operation of the T3B hardware components and the quality of the data while the acquisition of a run is still ongoing. It displays the captured waveforms of all activated oscilloscope channels, their integral and the integral of the waveforms captured in the IRM. Furthermore, the OM can show if all PS6403 oscilloscopes are running synchronously, meaning that they triggered the same number of events for a given spill. It can display a time distribution of the so far acquired statistics per spill and in total, and it can show a preliminary lateral hit profile in which the number of hits per T3B cell are histogrammed.

Pedestal shifts and instabilities in the SiPM operation such as a changing gain can be identified through the waveform integrals. Pick up noise through imperfect shielding manifests itself through spikes or interference signals in the waveforms. Problems with the beam quality such as an insufficient focussing manifest themselves in the hit profile. Lost spills manifest themselves in the statistics plots and general errors in the setup manifest themselves potentially in all plots. This is just a small selection of the potential problems at the test beam that can be noticed quickly by monitoring the data with the OM.