Gas Jet Target Research Articles

Feasibility study for precisely measuring the EIC He3 beam polarization with the Polarized Atomic Hydrogen Gas Jet Target polarimeter at RHIC

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is used to measure the absolute proton beam polarization, $\sigma_P^\text{syst}/P\!\lesssim\!0.5\%$, at the Relativistic Heavy Ion Collider. Here I consider the possibility of employing HJET to measure the ${}^3\text{He}$ ($h$) beam polarization at the Electron-Ion Collider (EIC). The dominant contribution to the ratio of the $h^\uparrow{p}$ and $p^\uparrow{h}$ analyzing powers, which is needed for such measurements, can be easily calculated using well-known values of the proton and helion magnetic moments, but some corrections should be applied to achieve the required accuracy. It was found that corrections due to absorption and ${}^3\text{He}$ breakup effectively cancel in the ratio and a correction due to hadronic spin-flip amplitudes can be derived from the proton beam measurements. As a result, the anticipated systematic uncertainty in the measured ${}^3\text{He}$ beam polarization can satisfy the EIC requirement $\sigma_P^\text{syst}/P\!\lesssim\!1\%$.

Electrodisintegration of 16O and determination of astrophysical S-factors of the inverse reaction

We performed Monte Carlo calculations in a simple model that relates the radiative capture and electrodisintegration reactions and showed that by using a windowless gas jet target and modern energy-recovery linear accelerators (ERLs, CBETA at Cornell, MESA at Mainz, ARIEL e-linac at TRIUMF) to reach high luminosity, a high precision measurement of the electrodisintegration of the 16 O nucleus would provide a method to determine the rate of the α on 12 C radiative capture with a superb statistical precision compared to existing data. The calculations were done for the beam energies of 30, 50 and 114 MeV and show a significant reduction in terms of statistical uncertainties for the energy range E c.m. < 2 MeV. The 114 MeV setting has the smallest statistical uncertainty, but at the same time the calculations for this beam energy setting were performed the furthest away from the real photon limit. The feasibility of this simple model still needs to be studied experimentally. This could be done with an experiment focused at Ec.m. > 2 MeV region, where the cross section is much larger.

First Experiments with CRYRING@ESR

The low-energy heavy ion storage ring CRYRING was transported from Stockholm to Darmstadt, modernized and reconfigured, and recommissioned as CRYRING@ESR. The machine is now in operation with all installations in service and is available as a user facility for experiments proposed through the SPARC collaboration. During the 2020–2022 period, we brought a number of experimental installations into service and used them to measure first data: the ultra-cold electron cooler for merged-beam electron–ion collisions, the gas jet target for atomic collisions, a next-generation microcalorimeter-based X-ray spectroscopy setup, and others. Ions can be injected either in low charge states from a local ion source through a 300 keV/u RFQ linac, or in high charge states from the GSI accelerator chain through ESR. This allows for very broad access to ions across the entire periodic table. CRYRING@ESR is able to de- or accelerate ions and cool and store beams of isotopically pure species in a desired charge state. While the analysis is still largely ongoing, the first experimental data already show that the machine reached its expected performance level, and our high expectations regarding achievable resolution in spectroscopy experiments have been fulfilled. With access to new classes of ions available through ESR injection and a new generation of experimental instrumentation, CRYRING@ESR is a unique facility for experiments with heavy, highly charged ions. Here, we will review our present setup and machine performance, discuss the data from our first commissioning experiments and briefly preview the upcoming new installations for the coming years.

Laser Wakefield Photoneutron Generation with Few-Cycle High-Repetition-Rate Laser Systems

Simulations of photoneutron generation are presented for the anticipated experimental campaign at ELI-ALPS using the under-commissioning e-SYLOS beamline. Photoneutron generation is a three-step process starting with the creation of a relativistic electron beam which is converted to gamma radiation, which in turn generates neutrons via the γ,n interaction in high-Z material. Electrons are accelerated to relativistic energies using the laser wakefield acceleration (LWFA) mechanism. The LWFA process is simulated with a three-dimensional particle in cell code to generate an electron bunch of 100s pC charge from a 100 mJ, 9 fs laser interaction with a helium gas jet target. The resultant electron spectrum is transported through a lead sphere with the Monte Carlo N-Particle (MCNP) code to convert electrons to gammas and gammas to neutrons in a single simulation. A neutron yield of 3×107 per shot over 4π is achieved, with a corresponding neutron yield per kW of 6×1011 n/s/kW. The paper concludes with a discussion on the attractiveness of LWFA-driven photoneutron generation on high impact, and societal applications.

Low- Q2 elastic electron-proton scattering using a gas jet target

In this paper, we describe an experiment measuring low-$Q^2$ elastic electron-proton scattering using a newly developed cryogenic supersonic gas jet target in the A1 three-spectrometer facility at the Mainz Microtron. We measured the proton electric form factor within the four-momentum transfer range of $0.01\le Q^2 \le 0.045(\text{GeV/c})^2$. The experiment showed consistent results with the existing measurements. The data we collected demonstrated the feasibility of the gas jet target and the potential of future scattering experiments using high-resolution spectrometers with this gas jet target.

A High-Density Polarized 3He Gas–Jet Target for Laser–Plasma Applications

A laser-driven spin-polarized 3He2+-beam source for nuclear–physics experiments and for the investigation of polarized nuclear fusion demands a high-density polarized 3He gas-jet target. Such a target requires a magnetic system providing a permanent homogeneous holding field for the nuclear spins plus a set of coils for adjusting the orientation of the polarization. Starting from a transport vessel at a maximum pressure of 3 bar, the helium gas is compressed for a short time and can be injected into a laser–interaction chamber through a non-magnetic opening valve and nozzle, thus forming jets with densities of about a few 1019 cm−3 and widths of about 1 mm. The target comprises a 3D adjustment system for precise positioning of the jet relative to the laser focus. An auxiliary gas system provides remote target operation and flushing of the gas lines with Ar gas, which helps to reduce polarization losses. The design of the target, its operation procedures and first experimental results are presented.

Improving a high-power laser-based relativistic electron source: the role of laser pulse contrast and gas jet density profile

A relativistic electron source based on high power laser interaction with gas jet targets has been developed at the Institute of Plasma Physics and Lasers of the Hellenic Mediterranean University. Initial measurements were conducted using the ‘Zeus’ 45 TW laser with peak intensities in the range of 1018–1019 W cm−2 interacting with a He pulsed gas jet having a 0.8 mm diameter nozzle. A significant improvement of the electron signal was measured after using an absorber to improve the laser pulse contrast from 10−10 to 10−11. A high stability quasi-mono-energetic electron beam of about 50 MeV was achieved and measured using a magnetic spectrometer for pulsed gas jet backing pressure of 12 bar. Supplementary studies using a 3 mm diameter nozzle for backing pressures in the range of 35–40 bar showed electron beam production with energies spread in the range from 50 to 150 MeV. The pulsed jet density profile was determined using interferometric techniques. Particle-in-cell simulations, at the above experimentally determined conditions, support our experimental findings.

High-Resolution Table-Top NEXAFS Spectroscopy.

A table-top near-edge X-ray absorption fine structure (NEXAFS) spectroscopy system consisting of a soft X-ray source and an integrated spectrometer with a significantly improved resolution is presented. The soft X-ray source is based on a long-term stable and nearly debris-free picosecond laser-induced plasma generated in a pulsed krypton gas jet target. Photon energies ranging from 250 to 1000 eV can be used for the absorption spectroscopy of thin samples. The newly designed spectrometer accomplishes a spectral resolution of E/ΔE = 1535 at 430 eV, being close to typical synchrotron setups. Moreover, a simultaneous multi-edge analysis is possible. The performance of the new system is demonstrated by investigating the fine structure of the K- and L-absorption edges of various elements (carbon, calcium, oxygen, iron, nickel, and copper) for different types of samples. An excellent agreement with synchrotron spectra is achieved.

Investigation of the emission properties of gas-jet targets in the water transparency window&amp;quot; of 2.3-4.4 nm under pulsed laser excitation

The article considers the results of studying the emission radiation of Ar, Kr, CO2, CHF3, CF4 and N2 gas jets excited by pulsed laser radiation. The shape of the spectral dependence in the spectral range 2.3-4.4 nm and the emission intensity of a number of lines in absolute units were studied. To excite the targets, a Nd : YAG laser, λ=1064 nm, tau=5.2 ns, Eimp=0.8 J was used. A supersonic conical nozzle with dcr=450 μm, 2α=11o, L=5 mm was used to form a pulsed gas jet. The pressure at the nozzle inlet was 25 bar, which corresponds to the developed condensation of molecular gases in gas jets. The spectra were deciphered and the ions emitting under the given experimental conditions were determined. Keywords: gas jets, shock waves, extreme ultraviolet radiation, emission spectra, laser plasma, X-ray spectrometer monochromator.

Absorption of laser radiation in a laser-produced plasma of Xe: hydrodynamic effects and nonequilibrium ionization

In this paper, experiments on measuring absorption of infrared laser radiation in the laser-produced plasma of Xe are described. An absorbed fraction of up to 65% was obtained when the gas-jet target was illuminated by a wide, defocused beam, whereas it barely reached 8.5% in the case of a sharply focused beam. The phenomenon is explained on the basis of a hypothesis of the plasma’s hydrodynamic expansion according to which the plasma leaves the illuminated area faster the smaller its size. This explains the similarity of extreme ultraviolet output and laser energy absorption as functions of the laser beam diameter. Based on the experimental results, an attempt to estimate the plasma parameters (N, T, <Z>) is undertaken, with the mean ion charge, <Z>, being calculated using ionization cross-sections for ions from +7Xe to +14Xe, which were obtained by means of a quantum-mechanical numeric simulation especially for the present work.

Laser-driven collisionless shock acceleration of protons from gas jets tailored by one or two nanosecond beams

It was proposed recently that laser-ion acceleration in gas jets may be significantly improved if each side of a gas jet target is tailored by an auxiliary nanosecond laser pulse [Marquès et al., Phys. Plasmas 28, 023103 (2021)]. In the present study, the proton acceleration by electrostatic shock in these one- or two-side tailored plasmas is investigated using particle-in-cell simulations. It is demonstrated that the formation of a thin plasma layer with a steep density profile and a maximum density of the order of the critical density strongly improves the proton acceleration in the forward direction with a maximum ion energy of tens of MeV with mildly relativistic laser pulses. Proton acceleration up to tens of MeV is predicted using realistic plasma density profiles obtained from tailored gas jet targets compared to a few MeV reported in other publications.

Charge exchange radiation diagnostic with gas jet target for measurement of plasma flow velocity in the linear magnetic trap

The study of longitudinal fluxes of energy and particles is one of the most important fundamental problems in the physics of open magnetic traps. The solution to this problem is the key to the successful implementation of fusion power in linear magnetic systems. The plasma electrostatic ambipolar potential largely determines the physics of longitudinal transport of particles and energy. In this work, we used the spectroscopic method CXRS (Charge eXchange Recombination Spectroscopy) to measure the plasma ion velocity distribution via the analysis of light emitted in this atomic process. The experiments were carried out in the gas dynamic trap (GDT), which is a linear plasma confinement system with an axially symmetric magnetic field configuration. We measured plasma potential and ion temperature of two plasma components: the main (hydrogen and deuterium) and the helium impurity. The paper presents the emission spectra of the lines H-α (656.28 nm) and He-I (667.8 nm). This method was applied for the first time to measure the spatial profile of the ambipolar potential in an open magnetic trap.

Operation and characterization of a windowless gas jet target in high-intensity electron beams

A cryogenic supersonic gas jet target was developed for the MAGIX experiment at the high-intensity electron accelerator MESA. It will be operated as an internal, windowless target in the energy-recovering recirculation arc of the accelerator with different target gases, e.g., hydrogen, deuterium, helium, oxygen, argon, or xenon. Detailed studies have been carried out at the existing A1 multi-spectrometer facility at the electron accelerator MAMI. This paper focuses on the developed handling procedures and diagnostic tools, and on the performance of the gas jet target under beam conditions. Considering the special features of this type of target, it proves to be well suited for a new generation of high-precision electron scattering experiments at high-intensity electron accelerators.

Emission Spectra of Molecular Gases N2 and CO2 in the Range of 3–20 nm upon Pulsed Laser Excitation of Various Gas-Jet Targets

Emission Spectra of Molecular Gases N2 and CO2 in the Range of 3–20 nm upon Pulsed Laser Excitation of Various Gas-Jet Targets

Sliding-wave acceleration of ions in high-density gas jet targets.

A hybrid mechanism of ion acceleration is investigated which demonstrates the higher spectral density of protons at high energies. The interaction of few-cycle terrawatt laser pulses with near-critical density gas target is studied with the help of two-dimensional particle-in-cell simulation. The generation of few MeV protons with high spectral concentration near cutoff is attributed to the propagation of solitary waves in the decaying density profile of the gas jet. Plasma dynamics at longer time scale is explained by semianalytical modeling and conditions for solitary wave breaking are presented.

Charge exchange radiation diagnostic with gas jet target for measurement of plasma flow velocity in the linear magnetic trap

The ambipolar electrostatic potential rising along the magnetic field line from the grounded wall to the centre in the linear gas dynamic trap, rules the available suppression of axial heat and particle losses. In this paper, the visible range optical diagnostic is described using the Doppler shift of plasma emission lines for measurements of this accelerating potential drop. We used the room temperature hydrogen jet puffed directly on the line of sight as the charge exchange target for plasma ions moving in the expanding flux from the mirror towards the wall. Both bulk plasma protons and He2+ ions velocity distribution functions can be spectroscopically studied; the latter population is produced via the neutral He tracer puff into the central cell plasma. This way, potential in the centre and in the mirror area can be measured simultaneously along with the ion temperature. A reasonable accuracy of 4 ÷ 8% was achieved in observations with the frame rate of ≈1 kHz. Active acquisitions on the gas jet also provide the spatial resolution better than 5 mm in the middle plane radial coordinate because of the strong compression of the object size when projected to the centre along the magnetic flux surface. The charge exchange radiation diagnostic operates with three emission lines: H-α 656.3 nm, He-I 667.8 nm and He-I 587.6 nm. Recorded spectra are shown in the paper and examples for physical dependences are presented. The considered experimental technique can be scaled to the upgraded multi-point diagnostic for the next generation linear traps and other magnetic confinement systems.

Progress on internal gas-jet target nuclear reaction at the HIRFL-CSR

Direct nuclear reactions induced by light ions, e.g., proton and alpha particles, have been investigated for about a century since the Geiger-Marsden experiment in 1908. It provides important information on nuclear structure and nuclear astrophysics. For instance, neutron skin thicknesses of nuclei determined by using proton and α elastic scattering play an important role in constraining the equation of state (EOS) of isospin asymmetric nuclear matter. These reactions were mostly conducted in direct kinematics, that is to say, the light-ion beam from accelerator interacts with a target made of the nuclei of interest. Obviously, such kinds of experimental investigations are limited to stable solid isotopes without active chemical property and radioactivity, due to the difficulty to make unstable targets. To test theoretical models developed from stable nuclei and explore new physical phenomenon on exotic nuclei, it is essential to investigate direct reactions on nuclei far from stability. As a result, experimental method based on inverse kinematics, namely active gas target technique, has been developed, where the unstable nuclei of interest produced by radioactive ion beam facilities collide with hydrogen and helium gases in a bubble chamber. The direct reactions are performed in inverse kinematics. One advantage is that low energy recoils at small center of mass angles can be measured easily at relatively large laboratory angles. However, this experimental method is insensitive to detect scattering recoils with energies of a few hundred keV, due to measurement based on gas detector. In recent years, a novel experimental method, namely study with stored beam in storage ring interacting with internal gas-jet target, has attracted much interest. It was proposed firstly for the exotic nuclei studied with light-ion induced reactions in storage rings (EXL) project. The technique is based on the internal gas-jet target instead of active gas target. It is an important supplementary experiential method for studying direct nuclear reactions induced by light ions, which is characterized by low-momentum sensitivity, high detection efficiency and low background. It is an ideal tool to study the isotopes with active chemical property and radioactivity. The cooler storage ring at the heavy ion research facility in Lanzhou (HIRFL-CSR) consists of a main cooler storage ring (CSRm) and an experimental cooler storage ring (CSRe). The two rings are connected by a radioactive ion beam line 2 (RIBLL2). The CSRe is equipped with an internal gas-jet target. As one of the existing facilities, the HIRFL-CSR provides an opportunity for performing in-ring direct nuclear reactions induced by light ions with the internal gas-jet target. Since 2016, a silicon strip detector compatibility with ultra-high vacuum in heavy-ion storage ring has been developed to build the in-ring direct nuclear reaction spectrometry at the HIRFL-CSR. A feasibility experiment on proton elastic scattering on 58Ni nuclei has been operated successfully by using the in-ring nuclear reaction spectrometry at the HIRFL-CSR. The nuclear matter distribution radius of 58Ni was extracted from measured differential cross sections at low momentum transfer. Proton elastic scattering experiment on 78Kr nuclei was also carried out to extract the nuclear matter radius at the beginning of 2021. In this paper, we report the development of in-ring direct nuclear reaction spectrometry at the HIRFL-CSR and corresponding experiments. Research plans in the (near) future, especially for measuring nuclear matter distribution radius of 133Cs, are also introduced.

Application of Nomarski interference system in supersonic gas-jet target diagnosis

Supersonic gas-jet target performs an important role in laser wakefield acceleration, and its density diagnosis is a significant part of target characteristic study. In this paper, a Mach–Zehnder and Nomarski interference system is set up and used for gas-jet target density diagnosis. We have investigated and compared the performance of the Mach–Zehnder part and Nomarski part. The feasibility of the Nomarski interferometer with vertical fringes has been verified. Moreover, it shows better stability and has a more compact structure, beneficial for obtaining more accurate and effective target density characterization in laser wakefield acceleration.

Towards background-free studies of capture reaction in a heavy-ion storage ring

Stored and cooled, highly-charged ions offer unprecedented capabilities for precision studies in the realm of atomic, nuclear structure and astrophysics[1]. After the successful investigation of the 96Ru(p,7)97Rh reaction cross section in 2009[2], the first measurement of the 124Xe(p,7)125Cs reaction cross section has been performed with decelerated, fully-ionized 124Xe ions in 2016 at the Experimental Storage Ring (ESR) of GSI[3]. Using a Double Sided Silicon Strip Detector, introduced directly into the ultra-high vacuum environment of a storage ring, the 125Cs proton-capture products have been successfully detected. The cross section has been measured at 5 different energies between 5.5AMeV and 8AMeV, on the high energy tail of the Gamow-window for hot, explosive scenarios such as supernovae and X-ray binaries. The elastic scattering on the H2 gas jet target is the major source of background to count the (p,7) events. Monte Carlo simulations show that an additional slit system in the ESR in combination with the energy information of the Si detector will enable background free measurements of the proton-capture products. The corresponding hardware is being prepared and will increase the sensitivity of the method tremendously.

Spin-polarized proton beam generation from gas-jet targets by intense laser pulses.

A method of generating spin-polarized proton beams from a gas jet by using a multipetawatt laser is put forward. With currently available techniques of producing prepolarized monatomic gases from photodissociated hydrogen halide molecules and petawatt lasers, proton beams with energy ≳50 MeV and ≈80% polarization are proved to be obtained. Two-stage acceleration and spin dynamics of protons are investigated theoretically and by means of fully self-consistent three-dimensional particle-in-cell simulations. Our results predict the dependence of the beam polarization on the intensity of the driving laser pulse. Generation of bright energetic polarized proton beams would open a domain of polarization studies with laser driven accelerators and have potential application to enable effective detection in explorations of quantum chromodynamics.