IMXS

Experiment:

Intergalactic and Interstellar Medium X-ray Survey with a cryogenic Spectrometer on the international space station.- IMXS

Laboratory and beam: The International Space Station —ISS, Diffused Soft X-rays from space

Group composition:

N. ord. | Nominativo | Qualifica | Gruppo afferenza | Percentuale tempo
| SEZIONE DI GENOVA |  |  |
1 | GALLINARO Gaetano | P.A. | II | 50
2 | GATTI Flavio | R.U. | II | 20
3 | PALLAVICINI Marco | INFN Ric | II | 10
4 | PERGOLESI Daniele | Borsista | II | 50
5 | RAZETI Marco | Borsista | II | 50
6 | TESTERA Gemma | INFN Ric | II | 10
7 | VACCARONE Renzo | INFN I Ric | V | 20
8 | VITALE Sandro | P.O. | II | 40
9 | ZONDLOWSKI Maxime | Borsista CEE | II | 50
| IST. ASTROFISICA SPAZIALE -CNR ROMA TOR VERGATA |  |  |
1 | COSTA Enrico | Dir.Ricerca |  | 20
2 | PIRO Luigi | I Ric. |  |
3 | SOFFITTA Paolo | ric |  | 25
| OSSERVATORIO ASTRONOMICO TORINO |  |  |
1 | FERRARI Ottilio | P.O. Univ. TO |  |
2 | ORIO Marina | Ric. Astr. |  |
3 | TRUSSONI Edoardo | Astr. Ass. |  |
| LABEN S.p.A. |  |  |
1 | ZAMBRA Alberto | Resp. Area Scient. |  |

Letters of interest from D. McCammon (Wisconsin University at Madison) and from A.E. Szymkowiak (Goddard Space Flight Center)

1) Goal of the experiment:

IMXS will allow:

(a) the spectral survey of all the sky with unprecedented spectral energy resolution,

(b) the the measurement of the contribution of the warm intergalactic media to the baryonic content in the nearby universe,

(c) the first high resolution spectra of Gamma Ray Burst, (d) to disentangle the origin of the warm interstellar medium in our own Galaxy.

IMXS will provide a unique combination of very high spectral resolution, 4 eV FWHM in the 30-2000 eV range, and of large field of view, about 10°

The very high spectral resolution will allow to built-up a map of warm gas emission of as a function of the red shift. IMXS will be part of the payload of the International Space Station and will be operative from 1 to 3 years.

The ROSAT soft X-ray maps in the 1/4 keg band and 3/4 keg band are the only all scale survey data of the diffused soft x-ray radiation in the Universe.

We want to point out here the fact that the interpretation of the ROSAT data in the energy range below 1 keV is made difficult by the lack of spectroscopic information. The transition from a 3-color photometry to a spectroscopic X-ray astronomy is the necessary step in order to address the questions, which ROSAT and other previous experiments have introduced. The XQC sounding rocket program and the XRS detector demonstrated that the transition is now technically possible using cryogenic micro-calorimeters at 100 Mk in place of traditional detectors, but these experiments can study only limited region of the sky a properly selected sources.

The goal of the IMXS project is to apply this new technology to the study of the diffuse background in the energy range 30-2000 eV over all of the Sky. This exploration will resolve important questions about the role of hot gas in the interstellar and intergalactic medium, the galactic halo and nearby interstellar space that cannot be answered in any other way. In fact the energy resolution of 4 eV FWHM, the angular resolution of 10o and the 84% of sky coverage allowed by the ISS make IMXS the only experiment, at the state of the art, capable of a spectroscopic survey with sufficiently high statistics and sufficiently high sky coverage. IMXS will be able to separate spatially and spectroscopically the different diffuse galactic and extragalactic components. Line diagnostic will provide information of physical ionization state and the chemical composition of the warm media. In the lifetime of the mission we expect to observe about 3 bright Gamma Ray Burst. These will provide the unique opportunity to measure at high resolution the soft x-ray spectrum of Gamma Ray Bursts.

2) Physics achievements during 1999-2000

Studies were made to select the candidate detectors.

Significative improvements of noise characteristics of silicon termistor produced at Goddard promise a better resolution with respect to XQC arrays.

Preliminary feasibility studies where made on the Dewar system.

The use of cryogenerators to cool the thermal shields to temperatures around 40 K or lower (now produced in the industry), indicates that the cryogenic autonomy can be extended to years without superfluid helium refilling.

An ADR system with a very low fringe field is under study.

3) INFN contribution to the experiment in terms of manpower and financial support.

- Manpower: 9 researcher and graduated students (3 FTE) and support from the high technology workshop of the section.

- Financial support: 9 Ml for R&D

4) Number of publications in refereed journals: 1

5) Number of talks in conferences: 2

6) Number of undergraduate and doctoral thesis on the experiment:

n° 1

7) Leadership role in the experiment

Spokesperson of the IMXS experiment and proposed Principal Investigator to ASI is Sandro Vitale.

The design of the ADR system and of the detector array is responsibility of Flavio Gatti.

The dewar design is care of Renzo Vaccarone

8)Innovative instruments

Use of high-energy resolution micro calorimeters at energy below 2 KeV in space for a several years mission is a major challenge.

A particular effort is required to provide a cryogenic system providing the detectors operating temperature of about 40 mK for a few years in space

A Super fluid helium Dewar with a cryogenic autonomy as required is under design.

9). Comparison with other experiments

No other approved mission with similar energy resolution, field of view and exposed area are currently scheduled to be launched within 2004. Mission with comparable resolution (but obtained with dispersive spectrometers), which are currently, operating are Chandra and Newton XMM. However their limited field of view prevents them to make comparable measurements on diffuse emission and on Gamma Ray Burst prompt emission.

10) International committee, which has reviewed the experiment

The proposal was submitted to ASI and to INFN Commissione scientifica II