Negative Ion Time Projection Chamber Research Articles

Dual-Polarity Ion Drift Chamber: Experimental results with Xe–S[formula omitted] mixtures

A new experimental system was recently developed to measure the mobility of both positive and negative ions: the Dual-Polarity Ion Drift Chamber (DP-IDC). This system is intended to better understand the transport properties of ions in gases relevant for the performance of large volume gaseous detectors like the Negative Ion Time Projection Chambers (NITPCs). In this work, we present a description of the experimental setup and technique used, and the initial studies carried out in Xe–SF6 mixtures, whose interest has attracted attention as a possible alternative in searches for the neutrinoless double-beta decay.

On the properties of a negative-ion TPC prototype with GridPix readout

The performance of a GridPix detector to read out a negative ion TPC was studied using a module with four GridPix chips that are based on the Timepix3 pixelated readout ASIC. The quad module dimensions are 39.6mm×28.38mm, and the maximum drift distance is 40mm. The TPC is operated using a 93.6/5.0/1.4 gas mixture (by volume) of Ar/iC4H10/CS2 with a small amount of oxygen and water vapour at a pressure of 1030mbar and a temperature of 297K. Tracks were produced by a pulsed N2 laser. The GridPix chips are sensitive to single drift ions, and allow for the determination of the drift distance using the velocities of the different ion species. The 1.56ns time resolution of the Timepix3 chips allows for a precise determination of the drift properties in the longitudinal direction. The measured mobility of majority ion charge carriers is (1.391±0003) cm2/V/s. Using the high granularity pixel readout, the transverse and longitudinal diffusion coefficients were measured to correspond to an effective thermal diffusion temperature of 314 K and 384 K respectively. For 429 detected ions, the precision on the absolute drift distance is expected to be 1.33mm for a mean drift distance of 20mm.

MPGD simulation in negative-ion gas for direction-sensitive dark matter searches

Negative-ion time projection chambers (NITPCs) provide the absolute z-position from the arrival-times’ difference of several species of negative-ions. This is a strong background reduction method for rare event searches, such as direct dark mater searches. The characteristics of micro pattern gaseous detectors (MPGDs) in negative-ion gas were studied by both experiments and simulations to develop an NITPC for dark matter search experiments. An MPGD simulation method for the negative-ion gas with Garfield++, which has not yet been established, was developed. We present herein the MPGD simulation results in negative-ion gas, SF6 gas, together with the experimental results, such as gain, energy resolution, and signal creation from the MPGD for future NITPC optimization.

Negative Ion Time Projection Chamber operation with SF6 at nearly atmospheric pressure

We present the measurement of negative ion drift velocities and mobilities for innovative particle tracking detectors using gas mixtures based on SF6. This gas has recently received attention in the context of directional Dark Matter searches, thanks to its high Fluorine content, reduced diffusion and multiple species of charge carriers, which allow for full detector fiducialization. Our measurements, performed with a 5 cm drift distance Negative Ion Time Projection Chamber, show the possibility of negative ion operation in pure SF6 between 75 and 150 Torr with triple thin GEM amplification, confirming the attractive potentialities of this gas. Above all, our results with the mixture He:CF4:SF6 360:240:10 Torr demonstrate for the first time the feasibility of SF6− negative ion drift and gas gain in He at nearly atmospheric pressure, opening very interesting prospects for the next generation of directional Dark Matter detectors.

Study of Negative-Ion TPC Using μ-PIC for Directional Dark Matter Search

Negative-ion time projection chambers(TPCs) have been studied for low-rate and high-resolution applications such as dark matter search experiments. Recently, a full volume fiducialization in a self-triggering TPC was realized. This innovative technology demonstrated a significant reduction in the background with MWPC-TPCs. We studied negative-ion TPC using the μ-PIC+GEM system and obtained sufficient gas gain with CS2 gas and SF6 gas at low pressures. We expect an improvement in detector sensitivity and angular resolution with better electronics.

Photoelectron Track Length Distributions Measured in a Negative Ion Time Projection Chamber

We report photoelectron track length distributions between 3 and 8 keV in gas mixtures of Ne+CO2+CH3NO2 (260:80:10 Torr) and CO2+CH3NO2 (197.5: 15 Torr). The measurements were made using a negative ion time projection chamber (NITPC) at the National Synchrotron Light Source (NSLS) at the Brookhaven National Laboratory (BNL). We report the first quantitative analysis of photoelectron track length distributions in a gas. The distribution of track lengths at a given energy is best fit by a lognormal distribution. A powerlaw distribution of the form, f(E)=a(E/Eo)n, is found to fit the relationship between mean track length and energy. We find n=1.29 +/- 0.07 for Ne+CO2+CH3NO2 and n=1.20 +/- 0.09 for CO2+CH3NO2. Understanding the distribution of photoelectron track lengths in proportional counter gases is important for optimizing the pixel size and the dimensions of the active region in electron-drift time projection chambers (TPCs) and NITPC X-ray polarimeters.

Towards energy resolution at the statistical limit from a negative ion time projection chamber

We make a proof-of-principle demonstration that improved energy resolution can be obtained in a negative-ion time projection chamber, by individually counting each electron produced by ionizing radiation.

Background reduction and spin-dependent limits using DRIFT - a directionally sensitive dark matter detector

The DRIFT (Directional Recoil Identification From Tracks) collaboration operates a 1m3 low pressure gaseous negative ion time projection chamber (NI-TPC) WIMP dark matter search experiment in the Boulby Underground Laboratory. Recent progress from the DRIFT collaboration is presented that includes a series of background reduction work and the addition of CF4 to the target volume. A preliminary limit on the spin-dependent WIMP-proton interaction cross-section is presented from a non-blind analysis of 47.2 days live time with a 0.8 m3 30 Torr CS2 - 10Torr CF4 target. The preliminary limit has a minimum of 1.1 pb for a 100 GeV WIMP.

Gas Gain Measurements From a Negative Ion TPC X-ray Polarimeter

Gas-based time projection chambers (TPCs) have been shown to be highly sensitive X-ray polarimeters having excellent quantum efficiency while at the same time achieving large modulation factors. To observe polarization of the prompt X-ray emission of a Gamma-ray burst (GRB), a large area detector is needed. Diffusion of the electron cloud in a standard TPC could be prohibitive to measuring good modulation when the drift distance is large. Therefore, we propose using a negative ion TPC (NITPC) with Nitromethane (CH3NO2) as the electron capture agent. The diffusion of negative ions is reduced over that of electrons due to the thermal coupling of the negative ions to the surrounding gas. This allows for larger area detectors as the drift distance can be increased without degrading polarimeter modulation. Negative ions also travel ~200 times slower than electrons, allowing the readout electronics to operate slower, resulting in a reduction of instrument power. To optimize the NITPC design, we have measured gas gain with SciEnergy gas electron multipliers (GEMs) in single and double GEM configurations. Each setup was tested with different gas combinations, concentrations and pressures: P10 700 Torr, Ne+CO2 700 Torr at varying concentrations of CO2 and Ne+CO2+CH3NO2 700 Torr. We report gain as a function of total voltage, measured from top to bottom of the GEM stack, and as a function of drift field strength for the gas concentrations listed above. Examples of photoelectron tracks at 5.9 keV are also presented.

Low energy electron and nuclear recoil thresholds in the DRIFT-II negative ion TPC for dark matter searches

Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect of a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches.

The DRIFT-II Directional Dark Matter Detector

The DRIFT-II detector is a negative ion time projection chamber (NITPC) with the ability to measure nuclear recoils for the purpose of detecting dark matter, reconstruct three dimensional tracks of nuclear recoils, and has the potential to set competitive limits. The directional information provides powerful background discrimination and a means to robustly verify a dark matter signal as extraterrestrial in origin. DRIFT-II is designed to search for an anisotropic distribution of nuclear recoils as well as a daily modulation due to the rotation of the Earth. It is located in the Boulby Mine on the north-east coast of England at a depth of 1100 m (3300 m.w.e).

NITPC technical work in progress and sketch for a WIMP observatory

Direction-sensitive WIMP detection is important for conclusively identifying a halo-WIMP signal. It would also make possible the study of galactic halo dynamics through WIMP astronomy. A large low-pressure Negative Ion TPC (NITPC) is the only technique presently known which is capable of direction sensitive WIMP detection. Several advances in NITPC technology reported here. A new capture agent (CH3NO3) with several advantages over the standard CS2 is identified. Simulations with GARFIELD show that tracks completely contained within a single drift cell can be measured using the ‘‘radial drift chamber’’ structure proposed by Nygren. DRIFT I neutron source calibration data is shown in which the ‘‘head-tail’’ orientation of tracks is able to be determined. (Supported by the U.S. NSF under NSF-PHY-0300766.)

A negative-ion TPC with ultra-high energy resolution for 0-ν double beta decay search in 136Xe

Future searches for the neutrino-less double beta decay mode in candidate nuclei must confront the need for sensitivities at the level of 10 – 50 meV effective neutrino mass. Current techniques may not be able to scale simultaneously to the needed mass of active isotope with both improved energy resolution and much higher levels of background rejection. To address these severe challenges, a novel approach based on a negative-ion time projection chamber filled primarily with high-pressure 136Xe gas is developed. In addition to the provision of a nearly ideal active fiducial boundary surface, an energy resolution of ∼5 × 103 FWHM appears possible at the Q-value of 2.48 MeV. The background rejection advantages of detailed track information and a single monolithic detector are addressed. A barium daughter-tagging scheme based on mobility differences and a new approach addressing the goal of efficient electron capture and release in high-density gas exploiting chemical reactions are introduced. Many R&D issues are suggested by this new concept.

First operation of bulk micromegas in low pressure negative ion drift gas mixtures for dark matter searches

A bulk micromegas micropattern charge readout device has, for the first time, been operated at room temperature in low pressure carbon disulphide vapour. This is a key step opening prospects for use of micromegas readout for large volume negative ion time projection chambers (TPCs) without magnets, such as proposed for directional dark matter detectors and other rare event applications. The dependence of the gain on the amplification field, pressure and drift field has been evaluated. For the available gap size of 75 μm a maximum gain of 1300 ± 120 was achieved in 40 torr vapour with an energy resolution of 22% for 5.9 keV 55Fe X-rays. From a fit to the data, the Townsend coefficient gas parameters A and B have been derived. Operation has also been successfully achieved in xenon:carbon disulphide blends over a range of partial and total pressures. A gain of 890 ± 130 at an energy resolution of 35% has been recorded for a 1:1 blend at a total pressure of 80 torr. Possible improvements are discussed in the context of operation in directional dark matter TPCs as a replacement for multi-wire proportional counters.

Negative ion drift and diffusion in a TPC near 1 bar

Drift velocity and longitudinal diffusion measurements are reported for a Negative Ion TPC (NITPC) operating with Helium + CS 2 gas mixtures at total pressures from 160 to 700 torr. Longitudinal diffusion at the thermal-limit was observed for drift fields up to at least 700 V/cm in all gas mixtures tested. The results are of particular interest in connection with mechanical simplification of the DRIFT direction-sensitive Dark Matter search, and for high energy physics experiments in which a low- Z , low density, gaseous tracking detector with no appreciable Lorentz drift is needed for operation in very high magnetic fields.

Search for Axion-like Particles from the Sun in an Underground Negative-Ion TPC

Axion-like particles produced in the sun with masses in the keV range have been proposed to explain several long-standing anomalies in astrophysical X-ray observations. The gravitationally bound massive axions could be observed decaying to two X-ray photons in an instrumented underground detector volume. We propose to use a 1.5m 3 Negative-Ion TPC instrumented with GEM/Micromegas pad readout to perform a sensitive search for keV range axions. The sensitivity of the proposed experiment will be five orders of magnitude below existing limits after one year of running.

Low energy alphas in the drift detector

The Directional Recoil Identification From Tracks project is a US–UK endeavor to build and operate a low pressure negative ion TPC (NITPC) to search for weakly interacting massive particles (WIMPs) thought to make up the dark matter in our Galaxy. Low energy (∼10 keV) alpha events from U and Th decays within the walls and wires of the detector can enter the active volume of the detector and be confused for WIMP interactions. This paper presents data on and a model of low energy alphas in a NITPC operated at 40 Torr CS 2 with the aim of understanding and removing this potentially serious background. A comparison of the data to this model reveals good agreement with range predictions of SRIM2000 and allows us to calculate the energy dissipation per ion pair, W=19.0±0.5 eV for low energy alphas in CS 2.

Neutron recoils in the DRIFT detector

Abstract The Directional Recoil Identification From Tracks (DRIFT) project is an endeavor to build and operate a low pressure negative ion TPC to search for weakly interacting massive particles thought to make up the dark matter in our Galaxy. This paper will focus on a neutron exposure of a small DRIFT prototype, a Monte Carlo to simulate these events, and the derivation of the range and ionization as a function of energy for Sulfur and Carbon recoils in CS 2 gas.

Measurement of carbon disulfide anion diffusion in a TPC

A Negative Ion Time Projection Chamber was used to measure the field dependence of lateral and longitudinal diffusion for CS 2 anions drifting in mixtures of CS 2 and Ar at 40 Torr . Ion drift velocities and limits on the capture distance for electrons as a function of field and gas mixture are also reported.

Low pressure negative ion time projection chamber for dark matter search

Weakly interacting massive particles (WIMPs) are an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low pressure negative ion time projection chamber to search for WIMPs. The innovation of drifting ions, instead of electrons, allows the design of a detector with very high sensitivity and background rejection and a robust statistical signature for WIMP interactions.