Main Spectrometer Research Articles

The Mid-Infrared Instrument for the James Webb Space Telescope, IX: Predicted Sensitivity

We present an estimate of the performance that will be achieved during on-orbit operations of the JWST mid-infrared instrument, MIRI. The efficiency of the main imager and spectrometer systems in detecting photons from an astronomical target are presented, based on measurements at subsystem and instrument-level testing, with the end-to-end transmission budget discussed in some detail. The brightest target fluxes that can be measured without saturating the detectors are provided. The sensitivity for long-duration observations of faint sources is presented in terms of the target flux required to achieve a signal-to-noise ratio of 10 after a 10,000 s observation. The algorithms used in the sensitivity model are presented, including the understanding gained during testing of the MIRI flight model and flight-like detectors.

Focal-plane detector system for the KATRIN experiment

The focal-plane detector system for the KArlsruhe TRItium Neutrino (KATRIN) experiment consists of a multi-pixel silicon p-i-n-diode array, custom readout electronics, two superconducting solenoid magnets, an ultra high-vacuum system, a high-vacuum system, calibration and monitoring devices, a scintillating veto, and a custom data-acquisition system. It is designed to detect the low-energy electrons selected by the KATRIN main spectrometer. We describe the system and summarize its performance after its final installation.

Status of the KATRIN Experiment and Prospects to Search for keV-mass Sterile Neutrinos in Tritium β-decay

In this contribution the current status and future perspectives of the Karlsruhe Tritium Neutrino (KATRIN) Experiment are presented. The prime goal of this single β-decay experiment is to probe the absolute neutrino mass scale with a sensitivity of 200 meV (90% CL). We discuss first results of the recent main spectrometer commissioning measurements, successfully verifying the spectrometer's basic vacuum, transmission and background properties. We also discuss the prospects of making use of the KATRIN tritium source, to search for sterile neutrinos in the multi-keV mass range constituting a classical candidate for Warm Dark Matter. Due to the very high source luminosity, a statistical sensitivity down to active-sterile mixing angles of sin2θ < 1 . 10-7 (90% CL) could be reached.

Penning discharge in the KATRIN pre-spectrometer

The KArlsruhe TRItium Neutrino (KATRIN) experiment is a next-generation, large-scale tritium β-decay experiment to determine the neutrino mass by investigating the kinematics of tritium β-decay with a sensitivity of 200 meV/c2 using the MAC-E filter technique. In order to reach this sensitivity a low background level of 10−2 counts per second (cps) is required. A major background concern in MAC-E filters is the presence of Penning traps. A Penning trap is a special configuration of electromagnetic fields that allows the storage of electrically charged particles. This paper describes the mechanism of Penning discharges and the corresponding measurements performed at the test setup of the KATRIN pre-spectrometer. These investigations led to the conclusion that the observed electric breakdown, strong discharges and extremely large background rates were due to discharges caused by Penning traps located at both ends of the pre-spectrometer. Furthermore, the paper describes the design of a new set of electrodes (modified ground electrodes and new ``anti-Penning'' electrodes) to successfully remove these traps. After the installation of these electrodes in the pre-spectrometer, the measurements confirmed that the strong Penning discharges disappeared. The experience gained from the pre-spectrometer was used to design the electrode system of the main spectrometer. Recent measurements with the main spectrometer showed no indications of Penning trap related backgrounds.

Electron optical imaging properties of the KATRIN high field solenoid chain

In this work we study the imaging properties of the KATRIN solenoid chain from the center of the WGTS source to the symmetry point of the main spectrometer entrance solenoid by calculating the trajectories of 200 representative electrons numerically with the simulation package PartOpt. By using both the microscopic approach and the drift equations during the calculation, depending on the magnetic field strength, the calculation times could be reduced to several minutes per trajectory. The image of a cross-type start pattern is produced and it is shown that the maximal energy loss due to synchrotron radiation is less then 0.11eV.

Electromagnetic design of the large-volume air coil system of the KATRIN experiment

The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to determine the absolute neutrino mass scale with a sensitivity of 200 meV (90% confidence level) by measuring the electron energy spectrum close to the endpoint of molecular tritium β decay. Electrons from a high-intensity gaseous tritium source are guided by a strong magnetic field of a few T to the analyzing plane of the main spectrometer where an integral energy analysis takes place in a low field region (B < 0.5 mT). An essential design feature to obtain adiabatic electron transport through this spectrometer is a large volume air coil system surrounding the vessel. The system has two key tasks: to adjust and fine-tune the magnetic guiding field (low field correction system), as well as to compensate the distorting effects of the earth magnetic field (earth field compensation system). In this paper we outline the key electromagnetic design issues for this very large air coil system, which allows for well-defined electron transmission and optimized background reduction in the KATRIN main spectrometer.

Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment

The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. The source employs conversion electrons of 83mKr which is continuously generated by 83Rb. The K–32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7 eV) is shown to fulfill the KATRIN requirement of the relative energy stability of ±1.6 ppm/month. The sources will serve as a standard tool for continuous monitoring of KATRIN's energy scale stability with sub-ppm precision. They may also be used in other applications where the precise conversion lines can be separated from the low energy spectrum caused by the electron inelastic scattering in the substrate.

Modern Resonator Spectroscopy at Submillimeter Wavelengths

Classical resonator spectroscopy methods have been realized for the first time in the submillimeter wave range. A resonator spectrometer was developed earlier at the IAP RAS on the basis of an open Fabry-Perot resonator excited by the radiation of a backward wave oscillator whose frequency is stabilized by the phase lock loop system. This spectrometer is successfully used for high-precision measurements of the dielectric properties of solid, liquid, and gaseous dielectrics as well as for the metal and coating reflection measurements in the 36-370 GHz range. In this paper, we report an extension of the upper limit of the spectrometer operation frequency to 520 GHz. Features of operation of the main spectrometer systems in the extended frequency range are analyzed. The broadband measurements of absorption in modern MPCVD diamonds are presented. A continuous record of the absorption spectrum of the laboratory atmosphere in the 350-500 GHz range obtained for the first time by the high-sensitivity microwave method is demonstrated. Further prospects for extension of the spectrometer range to terahertz frequencies are discussed.

Stochastic heating by ECR as a novel means of background reduction in the KATRIN spectrometers

The primary objective of the KATRIN experiment is to probe the absolute neutrino mass scale with a sensitivity of 200 meV (90% C.L.) by precision spectroscopy of tritium β-decay. To achieve this, a low background of the order of 10−2 cps in the region of the tritium β-decay endpoint is required. Measurements with an electrostatic retarding spectrometer have revealed that electrons, arising from nuclear decays in the volume of the spectrometer, are stored over long time periods and thereby act as a major source of background exceeding this limit. In this paper we present a novel active background reduction method based on stochastic heating of stored electrons by the well-known process of electron cyclotron resonance (ECR). A successful proof-of-principle of the ECR technique was demonstrated in test measurements at the KATRIN prespectrometer, yielding a large reduction of the background rate. In addition, we have carried out extensive Monte Carlo simulations to reveal the potential of the ECR technique to remove all trapped electrons in a few ms with negligible loss of measurement time in the main spectrometer. This would allow the KATRIN experiment attaining its full physics potential.

A mobile magnetic sensor unit for the KATRIN main spectrometer

The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the electron neutrino mass with an unprecedentedsensitivity of 0.2 eV/c2, using β decay electrons from tritium decay. For the control of magnetic field in the main spectrometer area of the KATRIN experiment a mobile magnetic sensor unit is constructed and tested at the KATRIN main spectrometer site. The unit moves on inner rails of the support structures of the low field shaping coils which are arranged along the the main spectrometer. The unit propagates on a caterpillar drive and contains an electro motor, battery pack, board electronics, 2 triaxial flux gate sensors and 2 inclination senors. During operation all relevant data are stored on board and transmitted to the master station after the docking station is reached.

Energy calibration and monitoring of the KATRIN experiment

A new high precision voltage divider has been built for monitoring the analysing potential of the KATRIN main spectrometer. In addition a condensed 83mKr calibration source has been set up at the modified 1 eV resolving Mainz spectrometer, our measurements show that energy calibration and monitoring for KATRIN is feasible at the few ppm level.

Improved identification of clouds and ice/snow covered surfaces in SCIAMACHY observations

Abstract. In the ultra-violet, visible and near infra-red wavelength range the presence of clouds can strongly affect the satellite-based passive remote sensing observation of constituents in the troposphere, because clouds effectively shield the lower part of the atmosphere. Therefore, cloud detection algorithms are of crucial importance in satellite remote sensing. However, the detection of clouds over snow/ice surfaces is particularly difficult in the visible wavelengths as both clouds an snow/ice are both white and highly reflective. The SCIAMACHY Polarisation Measurement Devices (PMD) Identification of Clouds and Ice/snow method (SPICI) uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 μm to make a distinction between clouds and ice/snow covered surfaces, specifically developed to identify cloud-free SCIAMACHY observations. For this purpose the on-board SCIAMACHY PMDs are used because they provide higher spatial resolution compared to the main spectrometer measurements. In this paper we expand on the original SPICI algorithm (Krijger et al., 2005a) to also adequately detect clouds over snow-covered forests which is inherently difficult because of the similar spectral characteristics. Furthermore the SCIAMACHY measurements suffer from degradation with time. This must be corrected for adequate performance of SPICI over the full SCIAMACHY time range. Such a correction is described here. Finally the performance of the new SPICI algorithm is compared with various other datasets, such as from FRESCO, MICROS and AATSR, focusing on the algorithm improvements.

The Katrin experiment and the pre-spectrometer at reduced retarding potential

The KArlsruhe TRItium Neutrino experiment, KATRIN [21] will determine the mass of the ν ¯ e with a sensitivity of 0.2 eV (90% C.L.) via a measurement of the β -spectrum of gaseous tritium near its endpoint of 18.57 keV. An ultra-low background of a few mHz and an energy resolution of 0.93 eV are among the requirements to reach the sensitivity. These demands are fulfilled with the main spectrometer being of the MAC-E filter type and which is equipped with a 650 m 2 , two-layered and quasi-massless wire electrode presented in this article. We also report on a recent background related test experiment: the investigation of the possibility to reduce the retarding voltage of the pre-spectrometer in order to diminish a Penning trap leading to increased background.

Effect of a sweeping conductive wire on electrons stored in a Penning-like trap between the KATRIN spectrometers

The KATRIN experiment is going to search for the mass of the electron antineutrino down to 0.2 eV/c^2. In order to reach this sensitivity the background rate has to be understood and minimised to 0.01 counts per second. One of the background sources is the unavoidable Penning trap for electrons due to the combination of the electric and magnetic fields between the pre- and the main spectrometer at KATRIN. In this article we will show that by sweeping a conducting wire periodically through such a particle trap stored particles can be removed, an ongoing discharge in the trap can be stopped, and the count rate measured with a detector looking at the trap is reduced.

The KATRIN neutrino mass experiment

The Karlsruhe Tritium Neutrino experiment (KATRIN) aims to determine the electron neutrino mass from tritium decay in a model-independent way, by a kinematic measurement of the energy of β-electrons. The unprecedented sensitivity of 0.2eV/c2 will improve present limits by one order of magnitude. The decay electrons will originate from a 10m long windowless gaseous tritium source. Super-conducting magnets will guide the electrons through a differential and cryogenic pumping section to the electro-static tandem spectrometer (MAG-E-filter), where the kinetic energy will be measured. The experiment is presently being built at the Forschungszentrum Karlsruhe by an international collaboration of more than 120 scientists. The largest component, the 1240m3 main spectrometer, was delivered end of 2006 and first commissioning tests have been performed. This paper gives an overview of the goals and technological challenges of the experiment and reports on the progress in commissioning first major components. The start of first measurements is expected in 2012.

The wire electrode system for the KATRIN main spectrometer

Aims. KATRIN is a neutrino mass experiment based on the kinematics of tritium β -decay. This work presents the methods employed at KATRIN to reduce the spectrometer-related background. Methods. The electrode system of the main spectrometer includes a modular double-layer wire grid for electrostatic screening of background. The key features of the wire electrode and the underlying design criteria of the optimisation procedure are described. Status. Fabrication of the wire electrode modules is completed and installation into the KATRIN main spectrometer has started.

퓨리에 변환 적외선 분광기를 이용한 수직 분광 복사율 측정 장치의 제작과 측정

퓨리에 변환 적외선 분광기(FT-IR)를 이용한 물질의 적외선 분광 복사율 측정 장치를 구축하고 이 장치의 성능을 평가하였다. 본 장치는 기준 흑체, 시료 가열로, 광학계, FT-IR로 구성되어 있으며, 측정 온도 및 파장 영역은 <TEX>$200^{\circ}C{\sim}500^{\circ}C$</TEX>와 <TEX>$3.5{\mu}m{\sim}20{\mu}m$</TEX> 이다. 기준 흑체의 유효 복사율은 0.9993 이상으로 거의 1에 가까운 값을 나타내고 있었으며, 흑체의 분광 복사율에 대한 합성 상대 불확도는 0.69% 이하이다. <TEX>$300^{\circ}C$</TEX>에서 불투명한 알루미나, 흑연, 양극 처리된 알루미늄 시료의 수직 분광 복사율과, 금속(IMS200)의 표면 거칠기에 따른 복사율을 측정하였다. 금속(IMS200)의 표면 거칠기에 따른 복사율 변화는 거칠기가 증가할수록 증가하였다. An Instrument to measure normal spectral emissivity is built using a Fourier Transform-Infrared (FT-IR) spectrometer. The instrument is composed of four main parts, reference blackbody, sample furnace, optics system, and FT-IR spectrometer. Measurement ranges of temperature and wavelength are <TEX>$200^{\circ}C{\sim}500^{\circ}C$</TEX> and <TEX>$3.5{\mu}m{\sim}20{\mu}m$</TEX>, respectively. Measured emissivity of the reference blackbody is greater than 0.9993 with combined relative uncertainty less than 0.69%, which can be considered an ideal blackbody. We studied the emissivity of opaque alumina, graphite, anodized aluminum, and steel (IMS 200). It is shown that emissivity increases with the roughness of the steel (IMS 200) surface.

The wire electrode of the KATRIN experiment

The KArlsruhe TRItium Neutrino experiment, KATRIN will determine the effective mass of the e with a sensitivity of 0.2 eV (90% C.L.) via a measurement of the T2 beta-spectrum near the endpoint at 18.6 keV. An ultra-low background of a few mHz and an energy resolution of 0.9 eV are necessary in order to reach this sensitivity. To suppress secondary electron background from cosmic muons and from environmental radioactivity we will equip KATRIN's main spectrometer with a 650 m2 large, two-layered and quasi-massless wire electrode. The electrode has to be non-radiactive, non-magnetic, bakeable at 350°C and compatible with a vacuum of 10−11 mbar. The 248 modules of the electrode have to be produced with a mechanical precision of O(0.1) mm. We present the design, as well as the mass production and automated quality assurance of the electrode modules. This project is funded by the German Ministry for Education and Research (BMBF).

KATRIN focal plane detector

The KArlsruhe TRItium Neutrino experiment, with a proposed sensitivity of 0.20 eV (90% CL), aims to start taking neutrino mass data in 2010. The focal-plane detector and associated hardware are currently under construction. Like much of the experiment, this apparatus must conform to extremely high vacuum standards and high magnetic fields. The detector, a segmented Si PIN-diode array, will be calibrated with an electron gun and radioactive gamma sources. The detector backgrounds, which must be limited to 1 mHz, are reduced with a passive shield and a scintillator veto. The electronics, cooling, and data-acquisition system are currently being tested with prototype silicon detectors. Commissioning of the detector system in stand-alone mode will start at the University of Washington later this year, in parallel with Main Spectrometer tests in Karlsruhe. Design and status of each of the detector system components will be covered.

Hadronic particle identification with silicon detectors by means of d E/d x sampling

In order to study Generalized Parton Distributions (GPD) at future fixed-target Deep Inelastic Scattering (DIS) experiments, a detector is needed to observe particles at angles larger than can be covered by the usual forward-angle spectrometer used in this type of experiments. This additional (recoil) detector will determine the exclusivity of the measurements, which cannot be guaranteed by the main spectrometer due to its insufficient energy resolution. Within the limited space available in the target area of such an experiment, the recoil detector must accomplish particle identification as a stand-alone detector, up to particle momenta of 1.3 GeV c −1. Using Monte Carlo simulations it has been investigated to what extend an energy loss measurement with a small barrel shaped detector consisting of a few layers of silicon sensors can be used to realize this goal. It turns out that a rough estimate of the momentum is necessary in this case, which can be obtained by measuring the curvature of the tracks in the strong magnetic field employed by the polarized targets used in this type of experiments. Because these studies rely heavily on calculated energy loss distributions as produced by the Monte Carlo code, a beam test with a mixed proton-pion beam has been carried out at CERN to verify the results of the simulation. The beam test results presented here confirm the predicted particle identification capabilities of a detector based on multiple sampling of ionization tracks in silicon up to 1.3 GeV c −1.