1. to ENA detection for space mission Investigation on MPGD application
F. Pilo, C. Avanzini, G. Terreni- INFN Pisa-Italy
S.Orsini, E. De Angelis, R. Rispoli – IAPS-INAF Rome- Italy

2. ENA instrument schematic
Input
Analysis
Detection
Ions
ENA Photons Charged Particles e
ESA
Foil /surface
Stop/position detector
Time of Flight
Start detector

3. ENA detectors and their limits
The most used detectors for ENA in space are CEM, MCP and SSD.
CEM: able to provide signals for ToF systems. High efficiency. No space resolution.
MCP: Microchannel plates (MCPs) are compact electron multipliers developed in a surface (channels of ~2-12 microns). It is able to provide 1D-2D imaging, high gain (L/d). High spatial resolution (with appropriate anodes). No energy resolution.
SSD: able to provide energy information (pulse height analysis) for energy > tens keV.
> Up to now it has not been used a unique detector able to provide the requested informations (energy, mass, direction) in the pointed energy range of few keV up to hundreds keV
> The most used MCPs for imaging are very expensive and have a limit in dimension taking into account space launch vibration and intrinsic fragility of MCP glass

4. Open questions to address
1. Is the MPGD a good candidate for ‘Energetic’ Neutral Atoms (ENA) detection?
2. Is it possible to use MPGD in space? What is the development needed and the costrains to be overcome?
3. Why MPGD and why we are

5. 1. Feasability investigation: state of the art
Energy threshold of primary particles to generate enough electrons in the gas for MPGD
Simulation. First applied tools : geant4-garfiled and srim (as comparison)
a. primary particle (H+, O+) entering in the gas and number of electrons generated
b. feasable energy range (track lenght as a function of P, mixture) (i.e. Argon P=20mbar:1 atm)
c. propagation in the drift volume (overcome limit for the geant4 delta ray energy threshold)
from preliminary results it’s seems possible to find appropriate condition (input, gas, pressure, drift) to track this kind of primary particle

6. 1. Feasability investigation: state of the art
Entrance window. Can ionised ENA enter in the gas chamber mantaining requested information? Which kind of window material is needed?
Usually thin and ultrathin Carbon foil (0,5-3 mg cm-2) are used for ENA ionisation (in trasmission)
> good ionisation efficiency for H+ and O+
> energy straggling and angular scattering depending on the tickness
> graphene new candidate (Allegrini et al., JGR-SpacePhysics,2016)
Simulation. applied tools SRIM and Mulassys :
trasmission of H and O in the energy range 1-100keV with window of already used material (Si3N4, tickness
the goal is to find appropriate material also able to perform gas containment in space

7. 2. Actually in-flight Space Gas detector
Gas detectors for high energy particles have already flown.
In the energy range of our interest (few keV-hundreds keV) only few X- ray instruments are present, i.e.:
RXTE (PAC) (Xenon Proportional Array Camera)-1995
BEPPOSAX (HPGSPC) (Xenon/He)(Gas Strip Proportional Camera)-1996
INTEGRAL (JEM-X) (micro strip gas counter) (Xe/methane)-2002
IXPE (Gas Pixel Detector) (He)->to be launched 2020
Even for photons, some tecnological aspects for flight and space environmental condition are partially solved

8. Future purpose and next activity
Consolidate simulation and results
Confirm simulated feasability with test activity
Face possible background effect (i.e solar Ly-α photons)
Face technological constraints for space application (gas containment, window robustness, differential pressure, lifetime…)

10. Extra slides

11. ENA in ultrathin Carbon-foil
limit for a good application → 0.8 keV
Angular scattering at 1 keV
→ >10 degrees
Efficienza di ionizzazione : f(H+) = 5% per E=1keV f(H+) = 35% per E=30keV f(H0) = 1- f(H+) - f(H-) ~ 1 - f(H+)
someof the ENA particles are partially converted into positive and negative ions when stripping through an ultra-thin carbon foil (Figure 11). These ions can be revealed and analyzed by subsequent electrostatic deflection, thus providing ENA indirect information. Conversely, those neutrals that pass through the foil without ionization may be directly detected along their flow on a straight line.
H.O. Funsten, D.J. McComas, B.L. Barraclough,Opt.Eng. 32, 3090 (1993)
H.O. Funsten, D.J. McComas, E.E.Scime, Opt. Eng. 33, 349 (1994)
Elisabetta De Angelis
Master in Scienza e Tecnologia Spaziale Marzo 2017
Elisabetta De Angelis