ENA detection techniques: Instrument considerations Elisabetta De Angelis IFSI-INAF Rome, Italy Joint SERENA-HEWG Conference Santa Fe, May 12-14, 2008.

ENA detection techniques:Instrument considerations

Elisabetta De AngelisIFSI-INAF Rome, Italy

Joint SERENA-HEWG Conference Santa Fe, May 12-14, 2008

Outline

• Energetic Neutral Atoms instrument brief history

• Principal ENA generating processes

• ENA instrument schematic

• Low-Energetic Neutral Atoms case

Joint SERENA-HEWG Conference Santa Fe, May 12-14, 2008 2

The detection of ENA:Hystorical survey

• 1950 evidence of ENA in the Earth environment (Doppler shifted emission of H (6563 Å) in an aurora)• 1959• 1961• 1968 1° instrument that detect ENA (in situ). • 1971 failed experiment ( Mars 3/RIEP)• 1975 project not used (slotted disk velocity selector for LENA, J.H. Moore et al, Sp.Sci.Instrum. 1,377 , 1975)• 1982 IMP7,8 – ISEE 1 validation of remote sensing magnetosphere processes with ENA detection• 1985 1° ENA image from ISEE-1 (Roleof et al. JGR 90, 10991,1985)• 1990 ULYSSES (GAS)• 1991 CRRES• 1992 GEOTAIL (MICS)• 1995 ASTRID (PIPPI)• 1995 SAC/B (ISENA)• 1997 CASSINI (INCA)

New millenium

• 2000 IMAGE2000 IMAGE• 2003 MarsEXpress (Aspera3)2003 MarsEXpress (Aspera3)• 2003 Double Star (NUADU)2003 Double Star (NUADU)• 2005 Venus Express (Aspera4)2005 Venus Express (Aspera4)• 2006 Twins2006 Twins

To be launched To be launched

• 2008 Chandrayyan 2008 Chandrayyan • 2008 IBEX2008 IBEX• 2013 BEPI COLOMBO2013 BEPI COLOMBO

} study of ENA investigation possibility


1. Principal processes The charge exchange process

A generic charge exchange collision between energetic ions and neutral gas atoms can be represented by the following relation

where I1 + represents an ion of species 1, and A is an atom of species 2. The involved species could be the same, e.g., H+

+H→H+H+ (that is, one of the most common process in space plasma, given the presence of a great quantity of protons and Hydrogen). In figure a scheme of the process is showed.

2121 IAAI

ENA energy up to hundred keVENA energy up to hundred keV


1. Principal processes Sputtering process

max

min

,E

E

iieSi

H dEEEfdE

dRY

dE

d

If we consider the energy distribution of sputtered atoms fs(Ee,Ei) and the sputtering yield Y If we consider the energy distribution of sputtered atoms fs(Ee,Ei) and the sputtering yield Y (Lammer et al., 2003), we can calculate the flux of ENA originated via sputtering processes(Lammer et al., 2003), we can calculate the flux of ENA originated via sputtering processes

where R is the fraction of the considered species in the soil composition. where R is the fraction of the considered species in the soil composition.


Energy distribution function for sputtered particles of ejected Na

ENA energy of few eV up to hundred eVENA energy of few eV up to hundred eV

2. The ENA instruments

When we speak about an ENA instrument we should always specify the energy range of the instrument, because each design is chosen in order to accomplish a specific energy range. In fact, nowadays a unique detection technique for the entire ENA energy range doesn’t exist. It starts from few eV up to hundreds of keV, and such an extended range is able to acquire different information, useful for different environments. Conventionally, we can consider the ENA separated into three categories, depending on the energy range:

LENA (Low Energetic Neutral Atom) few eV- 1keVMENA (Medium Energetic Neutral Atom) 1keV – 30 KeVHENA (High Energetic Neutral Atom) 30 KeV- hundreds of KeV

The limits of these ranges are not frozen, and often they differ from each other or are partially superposed, but they will help us to distinguish the diverse techniques applied.


2. The ENA instruments:The IMAGE package

3 different energy ranges3 different solutions

2. ENA instrument schematic

Input Analysis Detection

Task

1. ENA direction

2. Photons rejections

3. Charged particles

deflection

1. Particle

identification

2. Energy analyses

1. Time of Flight

2. Energy resolution

Elements

and

Solutions

1. Sectored collimator to

have needed angular

resolution

2. Rejection techniques:

Filters-gratings-

photons/ENA trajectory

separation

3. Deflection plates

1. Carbon Foil or

conversion surface

generating

secondary electrons

2. Electrostatic

analyser for ionised

ENA

1. Start and Stop

detectors: 1-D, 2-D

MCP; SSD

2. Pulse height signal

or position detection


2. ENA instrument schematic

ENAPhotons

Charged Particles

Input Analysis Detection

Foil /surfaceESA

Stop/position detector

Time of Flight

Start element

Ions


e

3. L-ENA caseL-ENA Instrument techniques

A commonly used method to identify neutral atoms is to convert them to ionic one with a subsequent energy analysis of the ions by an electrostatic method.

Some Examples : LENA (Image), NPD (Aspera3-4), Chandrayaan-1, IBEX-Lo → conversion surf

IBEX-Hi → ultra-thin foils

This kind of instruments use an Indirect detection technique.The interaction element introduces uncertainty in terms of angular and energy scattering.

Joint SERENA-HEWG Conference Santa Fe, May 12-14, 2008

i+ i- n

Trasmission: ultrathin foilTrasmission: ultrathin foil

ENA

Reflection: conv. Surf.Reflection: conv. Surf.

i+ i- n

ENA

In particular interaction in transmission or in reflection with foil or conversion surface has been In particular interaction in transmission or in reflection with foil or conversion surface has been used in the L-ENA instruments.used in the L-ENA instruments.

10

ENA in ultrathin Carbon-foil

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+)

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)

Angular scattering at 1 keV→ >10 degrees


ENA– Conversion Surface : MgO example

(Scattering of Atoms and Molecules of a Magnesium Oxide Surface, M.Wieser,P. Wurz,K.Bruning, H. Heiland, NIM B,192, pp 370-380,2002)


L-ENA case

ENAPhotons

Charged Particles

Inpu t Analysis Detection

Stop/position detector

Time of Flight

Foil /surfaceESA

Ions

Start element

A Direct detection technique (without any conversion unit and/or electrostatic analysis) has not yet used in the low energy range for this instrumentation.The unique attempt of this phylosophy : J.H.Moore et al, Space Sci. Instr 1, 377, 1975 a slotted disk instrument with high power consumption, tested but not used for ENA

Shuttering Start system can be the good solution to have a direct Time-of-Flight analysis in the range of the low energetic neutral atoms


Micro-shuttering techniques:the ELENA example

STOP detector

Shuttering membrane

Position encoder

START section

ToF chamber

ENA flux

Fixed membrane

400 nm 20 m400 nm400 nm 20 m20 m

1. Scanning electron micrographs (SEM) images of one of the samples of Si3N4 membranes manufactured by the Institute of Photonics and Nanotechnology of CNR (Rome, Italy) (Orsini et al, in press)

2. Piezoelectric ultrasonic actuator (compact design, fast response and low power consumption) ranging up to 100 kHz

3. A capacitive based encoder has been studied to control the frequency and the instantaneous displacement of the ultrasonic shutter payload and the shutter phase, together with the alignment of the grids (Di Giulio, Engineering thesis)

The START SECTION

See Di Lellis presentation on Wednesday May1414

Direct detection of L-ENA

PRO• No interactions of ENA with any element preserve

information of energy and direction• Low weight and consumption• Photons can be distinguished from ENACONTRO• Detector efficiency at low energies• Limit on mass resolution• Photons can enter into the entrance with ENA and reach

detector


Conclusions

• From Scientific point of view the ENA detection has proved a great potentiality and now it promise new goals with the L-ENA detection

• From Technological point of view new solution has been solicited and the under development systems could open new possibilities of investigation.


ENA detection techniques: Instrument considerations Elisabetta De Angelis IFSI-INAF Rome, Italy Joint SERENA-HEWG Conference Santa Fe, May 12-14, 2008.

Documents

detection of ena

ena instruments

ena case

evidence of ena

ionised ena

flux of ena

ena instrument techniques

ena detection techniques