Thomas E. Berger

Performance characteristics of the MAMA detectors for the SUMER instrument on the SOHO Mission

We have initiated the characterizations of the Multi-Anode Microchannel Array (MAMA) detector systems for the European Space Agency/NASA Solar and Heliospheric Observatory (SOHO) mission. In this paper we briefly review the configurations of the SOHO MAMA detectors and describe their expected performance characteristics based on the results of characterizations of the curved-channel microchannel plates and of the initial characterization of the first engineering model detector system for the Solar Ultraviolet Measurements of Emitted Radiation instrument.

HiRES - High Resolution Extreme Ultraviolet Spectroheliometer toroidal diffraction grating performance evaluation

The HiRES sounding rocket payload has been described in detail in previous SPIE Proceedings. Here, optical design of the toroidal grating spectrograph is presented and discussed. Ray tracing results are presented which outline the extreme ultraviolet (EUV) performance theoretically attainable with the HiRES instrument. Effects of optical system misalignment on the spectrograph image quality are investigated. Laboratory test results of two f/15 toroidal diffraction gratings using a 1 meter vacuum spectrograph and a multi-anode microchannel array detector are presented and discussed. The test toroidal gratings are fabricated using the elastic substrate replication technique from a ruled master grating with either a 3600 lines/mm or 1800 lines/mm density. EUV images of 10 25 micrometers pinholes with 250 micrometers center-to-center spacing taken with a hollow cathode discharge lamp are presented. Interferometric studies of toroidal figure accuracy as well as optical and electron microscopy investigations into surface quality are presented and discussed. It is found that the current toroidal gratings exhibit good imaging characteristics across a wide wavelength range but suffer from excessive EUV scatter and spectral ghosting.

Stanford MAMA detector characterization facility

We have designed and fabricated a high-vacuum facility for the detailed characterization of the Multi-Anode Microchannel Array (MAMA) detector systems at Extreme Ultraviolet and Far Ultraviolet wavelengths between about 300 angstroms and 3000 angstroms. The first task for this facility is the characterization of the MAMA detectors for the European Space Agency/NASA Solar and Heliosphere Observatory (SOHO) mission. This paper describes the different configurations of the characterization facility and outlines the SOHO MAMA characterization procedures.

Spectroscopic characterization of the EUV toroidal grating for the HiRES rocket

The evaluation of the performances of a toroidal grating for the high-resolution EUV spectroheliometer (HiRES) has been realized. This is a holographically ruled grating operating in a normal incidence Rowland configuration at the 510 - 630 angstroms spectral range. An analysis of the grating resolution performances has been realized by means of a scintillator- intensifier-CCD detector showing very good results. Also a measurement of the grating diffraction efficiency has been performed, showing on the contrary a value lower than the predicted one.

Interferometric methods for assessment of toroidal diffraction grating performance

The measurement of the shape and optical performance of toroidal mirrors has always presented a challenge to the manufacturer and user of these types of optical elements. This report presents a technique for evaluating the complex shape and optical performance of long radius toroidal mirrors that are to be used in the EUV. The measurement techniques will be discussed and examples given. Interferometric analysis will be presented. Performance spot diagrams and MTF analysis will be discussed. Manufacturing techniques will be evaluated with respect to the application of more definitive measurement technology.

Design and test of a high-resolution EUV spectroheliometer

The HiRES High-Resolution EUV Spectroheliometer is a sounding rocket instrument yielding very high spatial, spectral, and temporal resolution images of the solar outer atmosphere, on the basis of a 45-cm Gregorian telescope feeding a normal-incidence stigmatic EUV spectrometer with imaging multianode microchannel-array detector system, as well as an IR spectrometer with imaging CCD detector system. Attention is given to the expected performance of this system, including the effects of vibrational misalignments due to the sounding rocket flight environment.

High-resolution stigmatic EUV spectroheliometer for studies of the fine scale structure of the solar chromosphere, transition region, and corona

We describe the design of a high-resolution stigmatic extreme-ultraviolet (EUV) spectroheliometer, configured for flight on a Black Brant sounding rocket, which consists of a 45-cm Gregory telescope coupled to a spectrometer employing a single toroidal diffraction grating in a normal-incidence Rowland circle mounting and an imaging pulse-counting Multi-Anode Microchannel Array (MAMA) detector system. The toroidal diffraction grating is fabricated by a new technique employing an elastically-deformable sub-master grating which is replicated in a spherical form and then mechanically distorted to produce the desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The spectroheliometer will produce spatially-resolved spectra of the chromosphere, transition-region and corona with an angular resolution of 0.4 arc sec or better, a spectral resolution AII of about 1O in first order, and a temporal resolution of the order of seconds. Because of the geometric fidelity of the MAMA detector system, the speciroheliometer will be able to determine Doppler shifts to a resolution of at least 2 mA at wavelengths near 600 A (-1.0 km s1), depending on the level of the accumulated signal. The unique characteristics of the spectroheliometer will be used in combination with plasma-diagnostic techniques to study the temperature, density and velocity structures of specific features in the solar outer atmosphere.

HiRES: a high-resolution stigmatic extreme ultraviolet spectroheliometer for studies of the fine-scale structure of the solar chromosphere, transition region, and corona

We describe the design of a high-resolution stigmatic extremeultraviolet (EUV) spectroheliometer, configured for flight on a Black Brant sounding rocket, which consists of a 45-cm Gregory telescope coupled to a spectrometer employing a single toroidal diffraction grating in a normalincidence Rowland circle mounting and an imaging pulse-counting multianode microchannel array (MAMA) detector system. The toroidal diffraction grating is fabricated by a technique employing an elastically deformable submaster grating that is replicated in a spherical form and then mechanically distorted to produce the desired aspect ratio of the toroidal surface for stigmatic imaging over the selected wavelength range. The spectroheliometer will produce spatially resolved spectra of the chromosphere, transition region, and corona with an angular resolution of 0.4 arcsec or better, a spectral resolution λ/Δλ of about 10 4 in first order, and a temporal resolution of the order of seconds. Because of the geometric fidelity of the MAMA detector system, the spectroheliometer will be able to determine Doppler shifts to a resolution of at least 2 ma at wavelengths near 600 a (~1.0 km s -1 ), depending on the level of the accumulated signal. The unique characteristics of the spectroheliometer will be used in combination with plasma-diagnostic techniques to study the emperature, density, and velocity structures of specific features in the solar outer atmosphere.