WP4 - Inner and central tracking with PID (Tracking TPCs)
WP Leaders:
- Diego Gonzalez Diaz
- Francisco Ignacio Garcia Fuentes
- Jochen Kaminski
Contact: DRD1-WP4-leaders@cern.ch
Participating institutes:
Universidade de São Paulo (USP), Carleton University (U Carleton), Institute of High Energy Physics (IHEP/CAS), Tsinghua University (U Tsinghua), Helsinki Institute of Physics (HIP), University of Jyväskylä (U Jyväskylä), IRFU, CEA, University Paris-Saclay (IRFU/CEA), University of Bonn (U Bonn), Technische Universität Darmstadt, Institut für Kernphysik (TUDa), GSI Helmholtzzentrum für Schwerionenforschung (GSI), Wigner Research Centre for Physics (RCP), INFN Sezione di Bari (INFN-Bari), INFN Sezione di Roma (INFN-Roma1), Iwate University (IU), European Organisation for Nuclear Research (CERN), Paul Scherrer Institut (PSI)
DESCRIPTION OF THE WORK PACKAGE
Time Projection Chambers (TPCs) have been extensively studied and used in many fields especially in particle, nuclear and neutrino physics experiments. Also smaller size TPCs are a good choice for beam diagnostics operating in high particle rate environments. The ECFA detector R&D roadmap (2021 report: CERN-ESU-017. CERN, 2020, p. 248. DOI: 10.17181/CERN.XDPL.W2EX) mentions in chapter 1 for gaseous detectors four Detector Research and Development Themes:
- DRDT 1.1 - Improve time and spatial resolution for gaseous detectors with long-term stability.
- DRDT 1.2 - Achieve tracking in gaseous detectors with dE/dx and dN/dx capability in large volumes with very low material budget and different readout schemes.
- DRDT 1.3 - Develop environmentally friendly gaseous detectors for very large areas with high-rate capability.
- DRTD 1.4 - Achieve high sensitivity in both low and high-pressure TPCs.
All four themes are relevant for the future developments of TPCs and therefore are priority topics in this work package. To improve time and spatial resolution (DRDT 1.1), MPGDs have already proven an excellent readout technology for TPCs as they improve the performance in all respects. The smaller feature size improves spatial resolution, a higher rate capability is reached and the ion backflow is reduced. The latter is an important aspect for TPCs to improve spatial resolution and stability, as the ions can introduce electrical field distortions in the drift volume. Therefore, TPCs are often operated in a gated mode, where a closed gating device is blocking ions from the gas amplification stage and is opened only on demand. New experiments require a continuous operation mode for increasing the fraction of sensitive time. MPGDs promise to reduce the ion backflow (IBF) by many orders of magnitude and therefore make a continuous operation a viable option.
Another advantage of TPCs is its contribution to PID by providing a precise dE/dx measurement, which can be further enhanced by cluster counting as pointed out by DRDT 1.2.
In particular highly pixelized readout structures like the GridPix, which is a combination of a Si-readout ASIC with a Micromegas gas amplification stage, feature the possibility of distinguishing single primary electrons, which can be used to record events with an unprecedented resolutions mentioned in DRDT1.1 and 1.2. For several future experiments like future e+e- collider or EIC a pixelTPC is considered as a possible tracker.
As low diffusion gases are needed for long drift distances, very specific quencher gases have been used sofar with low ωτ to reduce the transverse diffusion in magnetic fields. These gases often have a higher GWP (e.g. CH4: 28, CF4: 6630). The search for alternatives as described in DRDT 1.3 is also of high importance for this work package. While most tracking TPC are operated at atmospheric pressures, and changing the gas pressure (DRDT 1.4) is mostly used in applications of WP8, also tracking TPCs might consider experiment specific gas pressures deviating from atmospheric pressures. Therefore, this aspect will also be considered in one of the tasks along the studying gas mixtures.
TASKS AND DELIVERABLES
List of Tasks
T1: IBF reduction
Ion Backflow is defined as the number of ions reaching the drift volume over the number of ions created in the gas amplification. To minimize the electrical field distortions in the drift volume, the IBF has to be as low as possible. Depending on the experimental requirements active or passive measures to reduce the IBF can be taken. Most challenging is the passive reduction as only static fields can be used to guide the ions. This is necessary for a continuous readout of TPCs. In this task both approaches shall be studied to find solutions for both options.
T2: PixelTPC development
A highly pixelized TPC readout promises the best possible resolution in both space and energy only limited by the diffusion. Therefore, this approach should be studied in more detail in this task. Various approaches will be tested and the structures shall be optimized with respect to resolution and IBF.
T3: Optimization of the amplification stage and its mechanical structure, and development of low X/X0 field cages (FC)
One additional advantage of TPCs is their light and homogenous structure. Filled only with gas, they have no mechanical structures except the field cage (here both the electrical and mechanical aspects are referred to) and the endcaps. In this task new ideas shall be developed and investigated to further increase the homogeneity of the FC and to lower the material budget of both components.
T4: FEE for TPCs
The traditional TPC readout is based on a continuous sampling of the baseline and signals after an event trigger. This concept is not applicable any more for a continuous readout, but a self-triggered zero-suppressed readout has to be used. Nevertheless, sampling of the signals is highly favoured to identify double tracks, measure dE/dx more precisely and to get hints of the longitudinal diffusion. Standard tracking electronics does not fulfil these requirements and dedicated TPC electronics is necessary. Most of this electronics, however, is experiment specific and not easily available and usable. Therefore, this task is dedicated to develop an SRS-based readout system for smaller scale experiments and test setups with TPCs. It also includes the development of low power electronics and Front End Electronics cooling.
T5: Gas mixture
Because of the long drift distances (up to 2.5 m) specific gas mixtures with low diffusion coefficients are needed to improve the spatial resolution of a TPC. As most tracking TPCs are embedded in a magnetic field parallel to the electric drift field, gases with a high ωτ are sought, because the transverse diffusion is suppressed in this configuration. In this task new gases suitable for TPC applications are studied. A particular attention will be given to a low environmental impact (e.g. low GWP) and the effect of varying the gas pressure will also be studied.
List of deliverables
D1:
Demonstrator MPGD-TPC commissioned for studies of tracking performance at high rates using different types of amplification stages and readout electronics
This deliverable is related to the assembling of a TPC prototype, using any type of MPGD amplification stages and also readout electronics, to target high rate capability. This was based on the feedback given by most of the groups, where it was stated the assembling of various types of MPGD- based TPCs.
The main idea behind this deliverable is to group all the different prototypes into one, which can be available for different tracking studies and in synergy with the groups involved.
D2:
Report on Ion backflow studies as a function of particle rate including measurements and simulations for its reduction.
D3:
Report on the tracking performance with using high density readout electronics and different readout structures with large dynamic range.
D4:
Construction of new highly pixelized readout structures.
D5:
Develop new high-density electronics for TPCs for both pixelized and standard pad readout with low-power consumption, low noise, high dynamic range and cooling.
