Tracker-In-Calorimeter (TIC): a calorimetric approach to tracking gamma rays in space experiments

A multi-messenger, space-based cosmic ray detector for gamma rays and charged particles poses several design challenges due to the different instrumental requirements for the two kind of particles. Gamma-ray detection requires layers of high Z materials for photon conversion and a tracking device with a long lever arm to achieve the necessary angular resolution to separate point sources; on the contrary, charge measurements for atomic nuclei requires a thin detector in order to avoid unwanted fragmentation, and a shallow instrument so to maximize the geometric factor. In this paper, a novel tracking approach for gamma rays which tries to reconcile these two conflicting requirements is presented. The proposal is based on the Tracker-In-Calorimeter (TIC) design that relies on a highly-segmented calorimeter to track the incident gamma ray by sampling the lateral development of the electromagnetic shower at different depths. The effectiveness of this approach has been studied with Monte Carlo simulations and has been validated with test beam data of a detector prototype.Comment: 17 pages, 8 figures, 2 table

Measurement of the light component (p+He) energy spectrum with the DAMPE space mission

The DArk Matter Particle Explorer (DAMPE) is a space-based particle detector launched in a Sun- synchronous orbit on December 17th, 2015 from the Jiuquan Satellite Launch Center, in China. It has been taking data very smoothly for more than 5 years. Science goals of the DAMPE mission include the study of the electron-positron energy spectrum, the study of galactic cosmic-rays, gamma-ray astronomy, and indirect dark matter search. Performing precise measurements of light elements in space, the most abundant components of cosmic radiation, is necessary to address major problems in galactic cosmic ray acceleration and propagation mechanisms. Selecting a combined proton and helium sample (instead of proton or helium alone) allows larger efficiency and purity, also minimizing systematic effects in the reconstruction of the energy spectrum, due to possible cross-contaminations. The use of looser analysis cuts allows collecting larger statistics thus extending the covered energy range and providing a link between direct and indirect cosmic- ray measurements. The measurement of the p+He energy spectrum up to ∼ 150 TeV will be presented, along with a discussion on the features of the spectrum and a comparison with other experimental results

Observations of Forbush Decreases of Cosmic-Ray Electrons and Positrons with the Dark Matter Particle Explorer

The Forbush decrease (FD) represents the rapid decrease of the intensities of charged particles accompanied with the coronal mass ejections or high-speed streams from coronal holes. It has been mainly explored with the ground-based neutron monitor network, which indirectly measures the integrated intensities of all species of cosmic rays by counting secondary neutrons produced from interaction between atmospheric atoms and cosmic rays. The space-based experiments can resolve the species of particles but the energy ranges are limited by the relatively small acceptances except for the most abundant particles like protons and helium. Therefore, the FD of cosmic-ray electrons and positrons have just been investigated by the PAMELA experiment in the low-energy range (<5 GeV) with limited statistics. In this paper, we study the FD event that occurred in 2017 September with the electron and positron data recorded by the Dark Matter Particle Explorer. The evolution of the FDs from 2 GeV to 20 GeV with a time resolution of 6 hr are given. We observe two solar energetic particle events in the time profile of the intensity of cosmic rays, the earlier, and weaker, one has not been shown in the neutron monitor data. Furthermore, both the amplitude and recovery time of fluxes of electrons and positrons show clear energy dependence, which is important in probing the disturbances of the interplanetary environment by the coronal mass ejections

Performance of the DAMPE silicon-tungsten tracker-converter during the first 5 years of in-orbit operations

Since its launch, in December 2015, the satellite-based DAMPE (DArk Matter Particle Explorer) particle detector is taking data smoothly. The Silicon-Tungsten tracKer-converter (STK) of DAMPE consists of six tracking planes (6x, 6y) of single-sided silicon micro-strip detectors mounted on seven support trays. The STK is able to measure the charge and precisely reconstruct the track of traversing charged particles. Tungsten plates (1 mm thick) are integrated in the second, third and fourth tray from the top to serve as γ → e+e- converters. Commissioned rapidly after the launch, the STK is running extremely well since then. The STK in-orbit calibration and performance during its first more than 5 years of operation, including the noise behaviour and the thermal and mechanical stability, are presented in this contribution

Direct Measurement of the Cosmic-Ray Iron Spectrum with the Dark Matter Particle Explorer

Dark Matter Particle Explorer(DAMPE) is a calorimetric-type, satellite-borne detector for observations of high energy electrons, gamma-rays, and cosmic-ray nuclei. Using five years data collected with DAMPE from January 1, 2016 to December 31, 2020, we analyzed the spectrum of iron. Detailed studies of the fragmentation of iron in the detector have been performed using Monte Carlo simulations

Machine learning methods for helium flux analysis with DAMPE experiment

DAMPE is a space-borne experiment for the measurement of the cosmic-ray fluxes at energies up to around 100 TeV per nucleon. At energies above several tens of TeV, the electronics of DAMPE calorimeter would saturate, leaving certain bars with no energy recorded. It is also observed that at high energies the tracker and the scintillator detector that serve for the charge identification become heavily populated with back-splash tracks. Both effects interfere in precise measurements of the helium flux at highest energies. In the present contribution we discuss the application of machine learning techniques for the treatment of DAMPE data, to compensate the calorimeter energy lost by saturation and to identify helium events

Analyzing the Fermi Bubbles with DArk Matter Particle Explorer

The Fermi bubbles are two large structures above and below the Galactic Plane. They are first discovered by Fermi-LAT and thought to be related to the jet or the wind from the Galactic center. The DArk Matter Particle Explorer (DAMPE) is a space-borne high energy particle telescope aiming at measuring cosmic rays and photons in a broad energy range. In this work, we use 4.8 years of DAMPE photon data to search for the emission from the Fermi Bubbles. We calculate the TS values of the lobes and the significance of its curved spectrum. The obtained spectral parameters are then compared with those from the Fermi-LAT. We also search for the emission from the cocoon in the southeast part of lobes. Since the Galactic diffuse emission (GDE) model is a major source of systematic uncertainty, we also switch to the GDE models calculated with Galprop and evaluate the influence

Simulation of the DAMPE detector

Extensive Monte Carlo (MC) simulations are essential in understanding the detector’s response for high energy particle detection experiments. We present the infrastructure and status of MC simulations of the DArk Matter Particle Explorer (DAMPE), a satellite project for the direct detection of high-energy cosmic rays and gamma rays. The DAMPE simulation tool employs two widely used softwares, GEANT4 and FLUKA, which implement various physics lists to simulate the interactions of particles in the detector. The framework of the simulation tool, the production farms, the data-MC comparison, and the performance of MC simulations on the analysis are summarized