Liquid xenon detectors for particle physics and astrophysics

This article reviews the progress made over the last $20\text{years}$ in the development and applications of liquid xenon detectors in particle physics, astrophysics, and medical imaging experiments. A summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information is first provided. After an introduction of the different type of liquid xenon detectors, a review of past, current, and future experiments using liquid xenon to search for rare processes and to image radiation in space and in medicine is given. Each application is introduced with a survey of the underlying scientific motivation and experimental requirements before reviewing the basic characteristics and expected performance of each experiment. Within this decade it appears likely that large volume liquid xenon detectors operated in different modes will contribute to answering some of the most fundamental questions in particle physics, astrophysics, and cosmology, fulfilling the most demanding detection challenges. From detectors based solely on liquid xenon (LXe) scintillation, such as in the MEG experiment for the search of the rare “$\mu \to e\gamma$” decay, currently the largest liquid xenon detector in operation, and in the XMASS experiment for dark matter detection, to the class of time projection chambers which exploit both scintillation and ionization of LXe, such as in the XENON dark matter search experiment and in the Enriched Xenon Observatory for neutrinoless double beta decay, unrivaled performance and important contributions to physics in the next few years are anticipated.

Figure 1

Phase diagram of xenon.

Figure 2

High-resolution absorption spectra for solid Ar, Kr, and Xe in the range of the valence excitons. Volume and surface excitons are observed for all three samples. For Ar and Kr the results of surface coverage experiments are also shown. For Xe the experimentally determined spectrum in the range of the $n=1$ surface and volume exciton is displayed on an expanded scale together with a line-shape analysis. From 184.

Figure 3

Collected charge $(Q∕Q_0\mathrm{\%})$ as a function of electric field for ${}^{210}\mathrm{Po}$ in liquid xenon (squares) and ${}^{241}\mathrm{Am}$ in liquid xenon (circles) and liquid argon (triangles) (14).

Figure 4

Energy resolution and collected charge for $570\mathrm{keV}$ gamma rays in LXe as a function of electric field (13).

Figure 5

Ionization yield from nuclear recoils measured with small scale two-phase xenon detectors (labeled Columbia and Case) at different electric field (28).

Figure 6

(Color online) Field dependence of scintillation and ionization yield in LXe for $122\mathrm{keV}$ electron recoils (ERs), $56.5\mathrm{ke}{V}_r$ nuclear recoils (NRs) and $5.5\mathrm{MeV}$ alphas, relative to the yield with no drift field (28).

Figure 7

(Color online) Predicted electronic stopping power $dE∕dx$ for different particles in LXe, based on various references. The circles refer to the particle energies discussed by 28.

Figure 8

Density dependence of the energy resolution (% FWHM) measured for $662\mathrm{keV}$ $\gamma$ rays (52).

Figure 9

Electron drift velocity in gaseous and liquid xenon and argon, as a function of reduced electric field (169; 150; 207).

Figure 10

Influence of butane on the electron drift velocity in liquid xenon. Butane (○, 0.09%), (△, 1.4%), and solid line: pure xenon (207).

Figure 11

Mobility of positive holes in liquid xenon as a function of temperature (116).

Figure 12

Transverse and longitudinal diffusion coefficients for electrons in LXe as a function of electric field (84; 189).

Figure 13

Pulse height of $279\mathrm{keV}$ photopeak as a function of voltage for 2.9-, 3.5-, and $5.0\text{−}\mu \mathrm{m}$-diameter anode wires (80).

Figure 14

Relative photon yield of proportional scintillation and charge gain as a function of applied voltage to anode wires of different diameter. Solid lines are results of the fit by 80 to the data points in the region of the ionization chamber mode: (a) for $4\text{−}\mu \mathrm{m}$-diameter wire, (b) for $10\mu \mathrm{m}$, and (c) for $20\mu \mathrm{m}$ (144).

Figure 15

Rate constant for the attachment of electrons in liquid xenon $(T=167\mathrm{K})$ to several solutes: (△) $\mathrm{S}{\mathrm{F}}_6$, (◻) ${\mathrm{N}}_2\mathrm{O}$, and (○) ${\mathrm{O}}_2$ (39).

Figure 16

Collected charge $Q∕N_i$, where $N_i$ is the total ionization (number of electrons), for $P_o$ $\alpha$ particles as a function of applied electric field, in pure liquid xenon (●), and in liquid xenon doped with TMA (◼, $7\mathrm{ppm}$) and TEA (▲, $1\mathrm{ppm}$; △, $50\mathrm{ppm}$). The curves give the calculated results from Eq. (3) in 119.

Figure 17

Comparison between the energy spectra of ${}^{207}\mathrm{Bi}$ internal conversion electrons and gamma rays measured from ionization: (top) in pure liquid xenon and (bottom) in TEA-doped liquid xenon (119).

Figure 18

Emission bands in liquid rare gases, together with solid- and gas-phase spectra (126; 184).

Figure 19

Decay curves of scintillation from liquid xenon excited by electrons, $\alpha$ particles, and fission fragments, without an applied electric field (132; 118).

Figure 20

Decay curves of scintillation from liquid xenon with and without an electric field of $4\mathrm{kV}∕\mathrm{cm}$, (a) over a long time scale and (b) a short time scale. Note the change in time scale at $160\mathrm{ns}$ in (a) (132).

Figure 21

LET dependence of scintillation yield $Y$ in liquid argon (93, 96). Solid circles show the yields for relativistic particles. Nonrelativistic particles are represented by open circles. Open squares and triangles show the yields for nonrelativistic protons, whereas small open circles show those for nonrelativistic helium ions.

Figure 22

LET dependence of the ratio $(Q∕e+a{S}_r)∕(N_{\mathrm{ex}}+N_i)$ in liquid argon (93, 96). The label (f.f.) stands for fission fragments.

Figure 23

LET dependence of the scintillation yield in liquid xenon for various ionizing particles (203; 96).

Figure 24

(Color online) Relative scintillation efficiency of nuclear recoils in LXe (32, and references therein).

Figure 25

(Color online) Absorption coefficient for vuv photons in $1\mathrm{ppm}$ water vapor and oxygen and superimposed Xe emission spectrum (168).

Figure 26

Anticorrelation between scintillation intensity and collected charge in liquid argon for relativistic Ne ions (◻), Fe ions (○), La ions (△), and Au ions (×). The solid line is the theoretically estimated relation (145).

Figure 27

Energy resolution (FWHM) of La ions in LAr as a function of the electric field, measured separately from scintillation, ionization, and their sum (73).

Figure 28

Relation between $S_r∕S_{r_0}$ and $Q∕Q_0$ in liquid xenon (96). The straight line indicates the perfect anticorrelation of the charge and light signal. $\chi$ is the ratio of number of escaping electrons at zero electric field over the numbers of ion pairs produced by the ionizing radiation.

Figure 29

Schematic of a gridded ionization chamber. $d_1$ is the drift gap between the cathode (on the bottom) and the Frish grid, $d_2$ is the field region between the Frish grid and the anode (on the top).

Figure 30

Schematic of a $3.5\mathrm{l}$ LXe gridded ionization chamber, triggered by the scintillation light (23).

Figure 31

Schematic of an ionization chamber with coplanar electrodes. (a) Anode made of parallel strips. (b) Time variation of the induced charge signals and the resulting signal in case the charge $Q$ is collected onto the group of strips marked as $A$ (142).

Figure 32

An example of two-dimensional position-sensitive electrode, with orthogonal strips for collection and induction signals (63).

Figure 33

The energy spectrum of ${}^{22}\mathrm{Na}$ gamma rays measured with the gridded ionization chamber shown in Fig. 30 at $4\mathrm{kV}∕\mathrm{cm}$ drift field (23). The energy resolution of the $511\mathrm{keV}$ line is about 8% (FWHM).

Figure 34

The energy spectrum of ${}^{60}\mathrm{Co}$ gamma rays measured with the gridded ionization chamber shown in Fig. 30 at $4\mathrm{kV}∕\mathrm{cm}$ drift field (23). The energy resolution of the $1.3\mathrm{MeV}$ line is about 5% (FWHM).

Figure 35

Schematic of electrodes arrangement for an ionization calorimeter. (a) Gridded ionization chamber with a long sensitive region. (b) Multiparallel plate electrode system (86).

Figure 36

(Color online) Relation between energy resolutions and the estimated number of photoelectrons obtained for $\alpha$ particles and $\gamma$ rays (89, and references therein). The lower line expresses a relation of energy resolution which is inversely proportional to the square root of the number of photoelectrons. The upper line shows a worse energy resolution expected from the nonuniformity of light collection.

Figure 37

Schematic of the LXe scintillation prototype with $32\times 2\mathrm{in.}$ PMTs (Hamamatsu R6041Q) developed for the MEG experiment (147).

Figure 38

(Color online) Energy resolution $\left(1\sigma \right)$ as a function of gamma-ray energy, measured with the MEG detector. The data follow $1∕\sqrt{N_{\mathrm{phe}}}$ as expected (147).

Figure 39

(Color online) Schematic of a “sum signal mode” detector (30).

Figure 40

Light and charge as a function of drift field for ${}^{137}\mathrm{Cs}$ $662\mathrm{keV}$ $\gamma$ rays (30).

Figure 41

(Color online) Energy spectra of ${}^{137}\mathrm{Cs}$ $662\mathrm{keV}$ $\gamma$ rays measured with $1\mathrm{kV}∕\mathrm{cm}$ field in LXe, separately from charge and light (top panels) and from combined charge and light (lower panel, left); charge-light anticorrelation and its angle (lower panel, right) (30).

Figure 42

Schematic of the LXe-TPC. Left: Electrodes structure (not to scale). Right: Corresponding pulse shapes (21).

Figure 43

(Color online) Display of a $1.8\mathrm{MeV}$ $\gamma$-ray event with multiple Compton interactions, recorded with the LXe-TPC (21).

Figure 44

(Color online) Schematic of a two-phase xenon TPC.

Figure 45

Electron-extraction yield in LXe as a function of the electric field in the gas phase (25).

Figure 46

(Color online) A two-phase xenon detector’s response to AmBe neutrons (top) and ${}^{137}\mathrm{Cs}$ gamma rays (bottom), at $2\mathrm{kV}∕\mathrm{cm}$ drift field (28).

Figure 47

Schematic of a LXe-TPC as Compton telescope (26).

Figure 48

Mechanical drawing of the LXeGRIT TPC (26).

Figure 49

(Color online) Photo of the LXeGRIT TPC structure (cathode removed) (26).

Figure 50

The energy resolution of LXeGRIT as a function of energy, as measured in flight. The crosses and diamonds are data from two balloon flights (78).

Figure 51

(Color online) LXeGRIT image (reconstructed angles in degrees) of two calibration sources, ${}^{60}\mathrm{Co}$ and ${}^{60}\mathrm{Na}$, using a maximum likelihood imaging technique (31).

Figure 52

Schematic of the wire electrode system for the LXe ionization calorimeter for GeV gamma rays (94; 87).

Figure 53

(Color online) Photo of the different Hamamatsu PMTs developed for the XENON and XMASS dark matter experiments.

Figure 54

Schematic of the XENON10 detector (33).

Figure 55

The XENON10 detector purification system (33).

Figure 56

(Color online) Schematic of the XENON100 detector (11).

Figure 57

(Color online) Photos of the top and bottom PMT arrays of the XENON100 detector.

Figure 58

(Color online) Photo of the XENON100 detector installed in its shield (11).

Figure 59

(Color online) Schematic of the XENON1T detector.

Figure 60

(Color online) Schematic of the ZEPLIN II detector (6).

Figure 61

(Color online) Schematic of the ZEPLIN III detector (137).

Figure 62

(Color online) Schematic of the LUX detector (104).

Figure 63

(Color online) Schematic of the XMASS detector (200).

Figure 64

(Color online) Photo of the hexagonal PMT of the XMASS detector.

Figure 65

Schematic of the Russian LXe ionization calorimeter. (a) and (b) Inner (1) and outer (2) cylindrical vessel, (3) multiplate supports, (4) and (10) aluminum segments, (5) copper bar, (6) cryostat with $\mathrm{L}{\mathrm{N}}_2$, (7) electrode system, (8) HV connector, (9) Xe gas supply tube, (11) zeolite trap (46).

Figure 66

Energy and position resolution performance of the Russian LXe ionization calorimeter. (Left) Energy resolution dependence on electron energy. Crosses are the experimental points and circles are points from Monte Carlo simulations. (Right) Position resolution dependence on electron energy based on two different reconstruction algorithms. Full and open circles are data for two different position reconstruction algorithms, and the dashed and solid lines the corresponding predictions from simulation (46).

Figure 67

(Color online) Schematic of the Waseda multiplate LXe ionization calorimeter (162).

Figure 68

Schematic of a full length liquid xenon cell for light collection uniformity tests (65).

Figure 69

Relative light yield as a function of the distance from the Si photodiode, measured with cosmic-ray muons. Monte Carlo curves are shown for different light collimators (65).

Figure 70

Schematic of the MIT-ITEP-Dubna LXe scintillation calorimeter. (a) Unit cell of the calorimeter: 1, PMT; 2, fragment of p-terphenyl strip; 3, Mylar reflector. (b) Assembly of the full calorimeter reflector structure (2).

Figure 71

Schematic of the RAPID LXeTPC. TPC vessel with Ti window for incident $\gamma$ rays and quartz windows for PMTs (top) Cross section of the electrodes for charge readout (bottom) (57).

Figure 72

(Color online) Schematic of the large MEG prototype (146).

Figure 73

(Color online) Energy spectrum for $55\mathrm{MeV}$ gamma rays measured with the large MEG prototype (41).

Figure 74

(Color online) Photo of the full scale MEG LXe scintillation calorimeter.

Figure 75

(Color online) Schematic of the EXO-200 TPC (111). The length of the TPC as well as the diameter of the TPC planes are $40\mathrm{cm}$.

Figure 76

(Color online) Photo of one EXO-200 anode plane. Induction and charge collection grids cross at 120°. The LAAPD support platter is visible behind the grids (111).

Figure 77

Schematic of the Coimbra PET prototype (70).

Figure 78

The ministrip plate of the Coimbra PET prototype (192).

Figure 79

(Color online) Schematic of the Columbia LXe Compton PET unit cell (109).

Figure 80

(Color online) Schematic of the Columbia full scale LXe Compton PET (109).

Figure 81

(Color online) Schematic of the Nantes LXe Compton PET prototype (112).

Figure 82

(Color online) Arrangement of 32 PMTs in Waseda TOF PET prototype (158).

Figure 83

Schematic of the Waseda TOF PET prototype (158).

Figure 84

(Color online) Spatial distributions of $511\mathrm{keV}$ interaction points reconstructed with the Waseda prototype (88).

Figure 85

(Color online) Schematic of the Waseda full scale LXe TOF-PET (88).