A cryostat design for radiation damage experiments at low temperature

Abstract

A cryostat for electron irradiations at liquid hydrogen or helium temperatures is described. The cryostat uses two concentric liquid coolant containers, of which the inner reservoir is sealed and acts as a heat exchanger through ebullition and recondensation of the coolant gas. This allows irradiations with a power input from the beam of up to a few watts, and when the sample is thermally isolated allows it to be annealed up to room temperature.     

A system for doing low temperature-high pressure single crystal X-ray diffraction with a synchrotron source

Abstract

A new diamond anvil cell and a helium flow cryostat have been developed for X-ray diffraction on single crystals at low temperatures and high pressures using white radiation of a synchrotron beam. This novel instrument especially enables continuous change of temperature and pressure of the sample without any adjustment of alignment. Automatic search for diffraction peaks can be performed since less than 30 pm eccentricity can be maintained during the rotation of the cell in the cryostat and the rotation of the cryostat on the goniometer head. The minimum temperature reached is 46 K. Measurements of solid 4He at 11.8 GPa are presented which confirm the stability of the hcp phase on this isobar.     

A high-resolution Fourier transform spectrometer for far infrared magneto-optic spectroscopy of magnetic materials

We describe a high-resolution (0.015 cm⁻¹) Fourier transform spectrometer which has been developed to investigate bulk and surface magnetic polaritons in magnetic media by far infrared magneto-optic spectroscopy. The spectrometer uses a novel combination of laser-controlled sampling of the interferogram and phase modulation of the infrared beam to combine very accurate sampling and low signal-to-noise ratio. The spectrometer is coupled to a liquid helium cryostat with a 7 T superconducting magnet, and a liquid helium-cooled silicon bolometer is used as the detector. Samples can be mounted in the cryostat for polarised oblique incidence reflection measurements in the Voigt geometry with the applied magnetic field vertical. Measurements on surface polaritons are made by using attenuated total reflection (ATR) spectroscopy with silicon prisms to obtain the necessary wave vector enhancement. The resolution of the instrument is demonstrated with measurements on the rotational lines of water vapour, and a selection of measurements on a bulk single crystal of FeF₂, a uniaxial antiferromagnet, is presented to illustrate the performance of the instrument as a probe of magnetic excitations.     

A Homebuilt ESE Spectrometer on the Basis of a High-Power Q-Band Microwave Bridge

We present a Q-band spectrometer which was built recently at the Institute of Physical Chemistry of the University of Stuttgart. It allows us to perform the field-sweep electron spin echo (ESE), pulsed electron–nuclear double resonance (ENDOR), relaxation and electron spin echo envelope modulation experiments both at room and low (down to 1.5 K) temperatures. The spectrometer consists of an electromagnet, digital field controller, pulsed microwave bridge, probehead, cryostat, radio frequency unit, pulse programmer and data acquisition electronics. The Q-band microwave bridge with 10.8 W output power is based on a two-stage IMPATT-diode pulse amplifier. The commercial Varian electromagnet system is controlled by a 24-bit home-built digital controller. The external devices are interfaced to the two PCs via GPIB and LAN. The spectrometer control software was developed in Visual C++. It consists of two programs running synchronously on the control PCs. The spectrometer is equipped with a cylindrical TE₀₁₁ cavity constructed both for ESE and for pulsed ENDOR. The cavity fits into a liquid He cryostat thus allowing low-temperature experiments. An 8-bit data acquisition digitizer is used to collect the echo signals, and the PBESR-PRO-400 digital word generator orchestrates the pulse experiments and sets pulse sequences of the microwave bridge. The spectrometer performance is demonstrated on nitrogen impurities in a polycrystalline synthetic diamond, on silver clusters supported on NaA zeolite and electron-irradiated tooth enamel. Authors' address: Igor Tkach, Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany     

A stress tunable gallium doped germanium infrared detector system

A simple partable cryostat system for studying photoconductivity in semiconductors under variable uniaxial stress at liquid helium temperatures is described. It has been used with a Fourier transform spectrometer to determine the spectral response of the photoconductivity of gallium doped germanium between 10 and 140 cm^–1 as a function of stress and electric field. Details are also presented of the variation of breakdown voltage and dynamic resistance as a function of stress under low background conditions.     

A new fast type of Mössbauer spectrometer for the rapid determination of iron-bearing minerals used in the paint industry

A new miniaturised Mössbauer spectrometer has been developed for laboratory and industrial application. Equipped with a YAIO₃:Ce crystal fast scintillation detector unit and mini transducer for the energy modulation of gamma rays, the unique mechanical design enhances protection from radiation and prevents disturbance by mechanical vibrations. It can be used with various types of cryostat and furnace.Supported by the LabVIEW graphical programming environment and by the new algorithm for the quantification of iron-components, the spectrometer can be used as a single-purpose instrument for the rapid determination of the Fe²⁺/Fe³⁺ ratio in ilmenite and Morin transition temperature of hematite. It can also be used to monitor the manufacturing processes for titanium white and copperas red.     

Single crystal x-ray diffraction with a synchrotron source in a mdac at low temperature

Abstract

A new diamond anvil cell and a helium flow cryostat have been developed for x-ray diffraction on single crystals at low temperatures and high pressures using the white radiation of a synchrotron beam. This novel instrument especially enables continuous change of sample temperature and pressure without any adjustment of alignment. A minimum temperature of 46 K has been reached.

Presented at the IUCr Workshop on ‘Synchrotron Radiation Instrumentation for High Pressure Crystallography’, Daresbury Laboratory 20-21 July 1991     

Microcombustion of ng Amounts of Carbon in Non-Volatile Materials for isotope Ratio Evaluation

Abstract

A novel microcombustion technique for carbon isotopic analysis of nanogram amounts of carbon in non-volatile materials based on isotope ratio monitoring (irm) mass spectrometry is described. Liquid or solid samples placed in a quartz sleeve are combusted at 1000°C in a continuous stream of helium and oxygen. CO₂ removed from the carrier gas stream by cryogenic trapping is transferred onto a GC column. Following GC separation, the CO₂ is transferred via an open split to the ion source of a gas isotope ratio mass spectrometer. Reproducibility for samples >25 nmol carbon is <1‰. Problems associated with blanks from various sources and with reproducible deposition of small sample amounts led to variable accuracy, which was dependent on the compound class being analysed. Minimum sample size was in the range from 5 to 10 nmol carbon. Measurements of dissolved organic carbon (DOC) of groundwater from Germany yielded consistent values of δ¹³C = -28.8‰.     

Fabrication and testing of the recoil mass spectrometer at Bombay Pelletron

A recoil mass spectrometer (RMS) has been designed, fabricated and installed at the 15° S beam-line of the Pelletron at TIFR. The RMS consists of a quadrupole doublet just after the target chamber followed by an ‘electrostatic deflector’, a magnetic dipole and a second electrostatic deflector. The recoils produced in the ¹²C + ⁵⁸Ni reaction using 60 MeV ¹²C beam were focussed with the help of electric and magnetic fields and detected in a strip detector placed at the focal plane of the RMS. Further testing of the spectrometer to obtain mass resolution and efficiency are in progress.     

High quality infrared (8 μm) diode laser source design for high resolution spectroscopy with precise temperature and current control

The performance of a tunable diode laser (DL) spectrometer is directly determined by the DL qualities and its tunability control. Emission characteristics are very sensitive to current and temperature drifts. In order to obtain a high quality source for spectroscopy, we designed our own liquid nitrogen cryostat containing the DL. Moreover we compared current and temperature control and we found that temperature tuning can be more efficient. We check and demonstrate it by recording SO₂ spectra in the 1168–1169 cm^–1 spectral region.     

Time-of-flight neutron spectrometer for micro sample studies under high pressure

Abstract

A new neutron spectrometer for investigations of elastic and inelastic neutron scattering on polycrystal microsamples under high pressure in diamond and sapphire anvils cells is described. The spectrometer is operating at the IBR-2 pulsed reactor at JINR. The time-of-flight method and ring-shaped multicounter detector are used to register the scattered neutrons. Parameters and methodical peculiarities of the device and the examples of experimental studies are given.     

Self-Broadening Coefficients of CH3D Spectral Lines in the P-Branch of the v2 Band at 2200 cm−1

Abstract

We report the pressure broadening coefficients of 18 lines of the P-branch of the v₂, band of CH₃D near 2200 cm^?1, obtained at room temperature, using a Fourier Transform spectrometer with a resolution of 0.006 cm^?1     

Absolute Intensities of Spectral Lines in the Q-Branch of the CH3D at Low Temperature

Abstract

We report the absolute intensities of 38 lines of the Q branch of the v₂ band of CH₃D near 2200 cm^?1, obtained at 98.3 K, using a Fourier Transform spectrometer with a resolution of 0.006 cm^?1     

Performance Improvement in Fiber-Optic Spectrometers Using Photonic Crystal Fibers

Abstract

Resolution enhancement of a high-speed fiber-optic spectrometer is investigated in this article. The operation of these types spectrometers is based on conversion of the spectral-domain signal into the time domain by a dispersive element. A photonic crystal fiber is used as a dispersive fiber in this spectrometer. Resolution enhancement of considered spectrometer with photonic crystal fibers is studied. The fiber loss and length minimization in this spectrometer are obtained. Simulation results show that an increase in resolution will cause a decrease in the speed of the spectrometer. Trade offs between resolution and speed are studied.     

Neutron spectrometer based on a proton telescope with electronic collimation of recoil protons

A prototype of a neutron spectrometer based on a gas proportional counter with recoil-proton registration is created at the Frank Laboratory of Neutron Physics at the Joint Institute for Nuclear Research (FLNP JINR) in Dubna. The spectrometer is developed to measure the kinetic energy of protons scattered elastically at small angles that are produced by (n, p) reaction in an environment containing hydrogen. The elaborated prototype consists of two cylindrical proportional counters used as cathodes. They are placed in a gas environment with a common centrally situated anode wire. Studies on the characteristics of the neutron spectrometer were conducted using ²⁵²Cf and ²³⁹Pu-Be radioisotope neutron sources. Measurements were made with monoenergetic neutrons produced by the ⁷Li(p, n)⁷Be reaction when a thin lithium target was bombarded with a proton beam from an EG-5 electrostatic accelerator, as well as with neutrons from the reaction D(d, n) ³He with a gas deuterium target.     

Simple device for dissolution and sample transfer for applications in spin-hyperpolarization

ABSTRACT

Rapid dissolution and transfer of samples are crucial steps in hyperpolarization methods such as dissolution dynamic nuclear polarization (dDNP) and quantum-rotor-induced polarization (QRIP). Here we introduce a simple and modular dissolution transfer device, and we demonstrate its application for QRIP. This device operates with low pressures and solvent volumes compared to state-of-the-art dDNP setups. On the other hand, transfer times are longer, although sufficient for ¹³C NMR spectroscopy. Our approach does not require an additional cryostat.     

Computer controlled diode laser spectrometer with a helium evaporation cryostat and spectroscopy of thev 3 vibration of NCO

A computer-controlled diode laser spectrometer for the 1200 to 2500 cm^–1 spectral region is described. The spectrometer has been applied to high resolution spectroscopy of the NCO radical at 5.2 m. The lead-salt diode lasers are cooled to their operating temperature with a temperature adjustable helium evaporation cryostat. Computer-controlled tuning procedures for the frequency tuning of the diode lasers have been developed; they are independent of tables describing the tuning characteristics of the diode lasers. 41 lines of the antisymmetric stretching-vibrationv ₃ of the linear NCO radical have been observed. We were able to detect vibration-rotation transitions in both² _1/2 and² _3/2 fine structure sublevels. These measurements led to the precise determination of additional molecular constants.     

Secondary ion emission from organic films under bombardment with a 32S beam at 3 MeV/A

Abstract

An experimental investigation of the secondary ion emission from organic films under heavy ion bombardment at high energies was carried out by using a time-of-flight mass spectrometer coupled to a Tandem heavy ion accelerator. Preliminary results obtained at 3 MeV/A are reported and discussed.     

First result for the neutrino magnetic moment from measurements with the GEMMA spectrometer

The first result obtained in the measurements of the neutrino magnetic moment at the Kalinin nuclear power plant with the GEMMA spectrometer is presented. A high-purity germanium detector of mass 1.5 kg placed at a distance of 13.9 m from the reactor core is used in the spectrometer. The antineutrino flux at the detector position is 2.73 × 10¹³ $ \bar \nu The first result obtained in the measurements of the neutrino magnetic moment at the Kalinin nuclear power plant with the GEMMA spectrometer is presented. A high-purity germanium detector of mass 1.5 kg placed at a distance of 13.9 m from the reactor core is used in the spectrometer. The antineutrino flux at the detector position is 2.73 × 10¹³ /(cm² s). The differential method is used to select events of electromagnetic antineutrino-electron scattering. The spectra taken in the reactor-on and reactor-off modes over 6200 and 2064 h, respectively, are compared. On the basis of a data analysis, an upper limit of 5.8 × 10⁻¹¹ μB was set on the neutrino magnetic moment μ _ν at a 90% C.L. Original Russian Text ? A.G. Beda, V.B. Brudanin, E.V. Demidova, C.Vylov, M.G. Gavrilov, V.G. Egorov, A.S. Starostin, M.V. Shirchenko, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 11, pp. 1925–1935.     

Submillimetre EPR spectrometer

A wide-band submillimetre EPR spectrometer is described. A set of tunable backward wave oscillators and quasioptic lens system enables one to operate in the frequency region 79–535 GHz. The sample is placed in a magnetic field of up to 1 T at 4.2 K. The spectrometer is intended for the investigation of EPR spectra of rare-earth ions in solids with zero field splittings of the ground states near the frequency of operation and/or electron systems with ag-factor exceeding 5. The spectrometer’s capabilities are demonstrated with an investigation of the EPR spectra of Dy²⁺ and Dy³⁺ ions in CaF₂. As a result the exact value of the zero field splitting between the ground Γ₈ quartet and the first exited Γ₇ doublet of Dy³⁺ in CaF₂, Δ=257±0.5 GHz, has been measured directly.