ImpCresst -- A versatile simulation tool focusing on solid-state detectors at keV energies

Abstract

We present ImpCresst, a Geant4-based Monte Carlo tool to simulate backgrounds from natural and cosmogenic radionuclides, and calibration signals in solid-state detectors and their response to it. It is tuned for a fast-evolving and heterogeneous detector environment with a focus on physics at the keV range. This tool was originally developed and validated by the CRESST collaboration; however, its flexibility and configurability make it suitable for other experiments with similar requirements. Key features of ImpCresst include the dynamic geometry implementation directly from CAD files, ROOT-based data persistency of the whole event topology and automatic metadata annotation for data provenance, and interfaces to various particle generators, particularly for radiogenic and cosmogenic radionuclides. It includes also a newly developed particle generator for radioactive bulk and surface contaminations which is completely independent of any user defined confinement volumes. The auxiliary tool CresstDS applies detector-specific energy and time resolution based on a user-provided data set of empirical parameterization. We discuss also how to manage an ImpCresst based workflow in an HPC environment based on Apptainer and nextflow.

Figures (12)

• Figure 1: Technical drawing of the Cresst experimental setup. The cryostat holding the liquid helium and nitrogen can be seen at the top. Below the cryostat, the carousel hosts the detector modules. The shielding consists of polyethylene, lead, copper, an active muon veto, and the airtight radon box used to prevent radon contamination from air.
• Figure 2: Simplified UML class diagram of the abstract base class DetectorPart and derived classes to implement the hierarchy of components of the Cresst setup. For the sake of simplicity, the parameters and return type of the methods are omitted.
• Figure 3: Example visualizations with Blender of geometry components that are available in ImpCresst: (\ref{['fig:vis:carousel37']}) shows Carousel37, i.e., the detector array of the most recent data taking run 37. It itself is implemented as Constructive Solid Geometry (CSG), but loads the detector modules from CAD files as objects of type CADReader, e.g., the "TUM93A" module (\ref{['fig:vis:tum93a:cad']}, exploded view). Compared to a CSG implementation of the same module as instance of type CRESST3Detector (\ref{['fig:vis:cresst3Module']}, cutaway view), the CAD implementation allows a higher fidelity with respect to the reality (\ref{['fig:vis:tum93a:pic']}, photography of an open module). Loading geometries directly from CAD files also allows rapid simulations of R&D projects like the potential future detector module "CmCube" (\ref{['fig:vis:cmCube']}, cutaway view; \ref{['fig:vis:cmCube:pic']}, photography of an open module) that may feature several target crystals kept in place within the detector housing only by their weight, see Angloher:2023a for details.
• Figure 4: Simplified UML object diagram illustrating the composition of two objects instantiated from subtypes of ExperimentalSetup: whereas FreeCarousel37 encapsulates the composition of the carousel of data-taking run 37 with the related detector modules, CresstAtLNGS considered in addition the full experimental setup at LNGS. The detector modules have to be of a subtype of CryogenicDetector, e.g., CRESST3Module.
• Figure 5: Materials of the implemented CresstAtLNGS setup randomly sampled at 1.0e7 points in the $x$-$z$-plane. At $y=\qty{0}{\cm}$, the left and right panels of the muon veto have a tiny gap, needed to open the setup. Hence, these panels are not visible in this plot.