Conclusion and outlook: • The MCP-IonCCD combination exhibits clear potential for 1D imaging and for charged-particle detection in dispersive analytical instruments

(from high vacuum to atmospheric pressure).

• The technology is directly extendable to 2D in the event that a 2D version of the IonCCD is built.

• The large MCP gain allows for miniature, low cost instruments for trace analysis or for transient process studies in the kilohertz regime.

• MCP-IonCCD experiments motivate the development of faster readout electronics to match the 2-kHz capability of the IonCCD chip.

• Potential improvements in spatial resolution can be achieved with new chip packaging to achieve flat detection surface, key for other applications.

• The desired speed improvement will increase the detector duty cycle, sensitivity, and dynamic range or share speed at a 2-kHz frame rate.

• More attention should be devoted to MCP parameters in order to design and/or select a more adequate MCP for use in this novel imaging scheme.

References: 1. Sinha, M. P. et al., "Miniature focal plane mass spectrometer with 1000-pixel modified-CCD detector array for direct ion measurement," Review of Scientific Instruments, vol. 76, pp. 1-8, 2005.

2. Hadjar, O. et al., "IonCCDTM for Direct Position-Sensitive Charged-Particle Detection: from Electrons and keV Ions to Hyperthermal Biomolecular Ions," Journal of the American Society for Mass Spectrometry, vol. 22, pp. 612-623, 2011.

3. Langstaff, D. P., et al., "A New Ion Detector Array and Digital-Signal-Processor-Based Interface," Measurement Science & Technology, vol. 5, pp. 389-393, Apr 1994.

4. Cubric, D. et al., "Parallel acquisition electrostatic electron energy analyzers for high throughput nano-analysis," Nuclear Instruments & Methods in Physics Research A, vol. 645, pp. 227-233, 2011.

5. Hadjar, O. et al., "Preliminary demonstration of an IonCCD as an alternative pixelated anode for direct MCP readout in a compact MS-based detector," Journal of American Society of Mass Spectrometry, vol. 23, pp. 418-424, 2012.

6. Hadjar, O. et al., "IonCCD Detector for Miniature Sector-Field Mass Spectrometer: Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection," Journal of the American Society for Mass Spectrometry, vol. 22, pp. 1872-1884, 2011-Oct 2011.

7. Torr, M. R. "Persistence of phosphor glow in microchannel plate image intensifiers," Applied Optics, vol. 24, pp. 793-795, 1985.

Acknowledgement: The authors acknowledge the support of OI Analytical for this research. The Authors would like to thank Dr. William C. Schnute, from Dionex, a brand of Thermo Scientific, for his financial support in building the proximity focus assembly. The authors would like to thank CMS

Field Products for technical support. The work was performed at CMS Field Products, a subsidiary of OI Analytical, within the Analytics Value Center of Xylem, Inc.

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Pixelated-Anode for Direct MCP Readout in Imaging Applications

Omar Hadjar, William K. Fowler, Gottfried Kibelka, Chad Cameron, Scott Kassan, Ken Kuhn

OI Analytical, 2148 Pelham Pkwy, Bldg. 400, Pelham, AL 35124 USA

1-6 eV

820-825 eV

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MCP

IonCCD

Phosphor

screen

CCD

WSA DLA Anode

Germanium

layer

Single particle detector:

space & time resolved detection

Charge integration detector:

space resolved detection

Part

icle

cou

nte

r

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arg

e in

tegra

tor

Position sensitive detectors (PSD)

Readout time MCP pulse width

WS

A -

DL

A

Photons (UV to IR)

keV ions/electrons

keV neutrals

eV ions/electrons

sub-keV electrons

Image-charge coupling

PMT / NVD

EOID

0.5 fA*

per pixel

> 103

LDR

*noise level of 9 counts

(dN) is assumed for 1 sec.

integration time

The IonCCD can be used for indirect charged-particle detection when coupled to a micro-channel plate

(MCP). The MCP boosts the signal, enhancing the sensitivity of the overall detector. In this mode the

IonCCD acts as a pixelated anode for MCP readout, analogous to delay line and strip and wedge resistive

anodes (DLA, SWA). The MCP-IonCCD will not compete with the above detectors but can be used in high

count rate conditions when no coincidence detection is required. Compared to the standard CCD, the

IonCCD offers more potential applications (numbered at right). The MCP-IonCCD, as compared to an

EOID system, should be attractive for many applications as the extra steps, limitations and additional

hardware associated with phosphor screens are avoided7.

The IonCCD was first designed as a

focal plane detector for simultaneous

ion detection in a scan-free, sector-field

type, Mattauch-Herzog geometry mass

spectrometer (MHMS). This goal

influenced most of the present IonCCD

specifications. However, the newly

discovered electron detection capability2

of the IonCCD might extend its use to

include electron energy analyzers4 in the

field of electron spectroscopy using

either planar or cylindrical mirror

geometry analyzers (PMA, CMA).

ESA

Photocathode

Tim

epix

103

Single

MCP

gain

X pixel

number

High Dynamic Mass Range

magnet geometry (HDMR)3.

SPIE 2012, Baltimore Defense, Security+Sensing

+2 kV

+0.9 kV

+90V

0V

ion

acceleration

electron

extraction

FWHM (pixels)

N+ : 7.9

OH+ : 7.5

H2O+: 8.8

N2+ : 7.2

O2+ : 7.7

N+ OH+

H2O+

N2+

O2+

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Published Technology and company Information

51 mm long focal plane (2126 pixels)

25 mm quality area

microchannel plate

Magnetic Sector

Introduction: The novel IonCCD™, a charged-particle-sensitive pixelated detector,1,2 was used as an anode to directly read out the electrons exiting from the back of a micro-channel plate (MCP). The IonCCD chip is a 51-mm-long linear array of 2126 pixels, each of 21-µm width and 1.5-mm height, resulting in a 24-µm pitch.

Both simulations and experiments were performed to assess MCP-IonCCD performance in the context of a chip-based one-dimensional anode for direct MCP readout3. The assembled MCP-IonCCD test apparatus consisted of a standard, off-the-shelf, 25-mm-diameter circular MCP. The IonCCD was mounted at proximity focus. The

IonCCD eliminates the requirement for a phosphorus screen (after glow and electrons-to-photons conversion), as well as the need for a transformer lens or fiber coupling, as commonly used in imaging devices such as electro-optical ion detector systems (EOIDs). Another advantage is the elimination of the rather high voltages (~5-kV)

that are typically needed for effective electron-to-photon conversion. Finally, the IonCCD should preclude any photon-scattering-induced spatial resolution degradation. Our early MCP-IonCCD tests showed that the MCP permits an immediate 103-104 gain, with virtually no additional noise beyond that attributed to the IonCCD alone.

The high gain allows the use of lower IonCCD integration times, which will motivate the development of faster IonCCD readout speeds (currently at 2.7 ms) to match the 2-kHz 1D chip. The presented detector system exhibits a clear potential not only as a trace analysis detector in scan-free mass spectrometry, ion mobility and electron

spectroscopy but more importantly as a means to achieve simpler, more compact and robust 2D imaging detectors for photon and particle imaging applications.

Experimental parameters:

13.5 µA electron emission

10-5 torr ionization pressure

1.2 kV ion acceleration

1 T permanent magnetic sector

0.2 T magnetic field at MCP

0.1 ms IonCCD integration time

3.6% IonCCD duty cycle

357 Hz acquisition rate

Ion Mobility SpectrometryLN

First demonstration of direct IonCCD readout of outgoing electrons from

an MCP in a miniature sector-field type, Mattauch-Herzog geometry mass

spectrometer (MHMS) for simultaneous detection of doubly charged Xe

isotopes5.

Aside from its use as an anode for MCP readout in high

vacuum applications, the versatile IonCCD detects

charges at all gas pressures up to atmospheric pressure

and beyond. This capability should be beneficial not

only in drift tube IMS imaging and in diagnostics for

R&D purposes, but more importantly in dispersed ion

detection, i.e., as a an array detector for dispersive type

IMS instruments.

The mass spectrum shown here (averaged over 100

frames) is the result of a direct sniff of human

breath. Note the limited mass range or pixel window

(1000 pixels) due to the small MCP size (25 mm).

The electrical potential diagram illustrated for this

experiment clearly shows that the IonCCD can be

floated to practical high voltage values. This feature

permits a broad range of IonCCD applications with

and without MCP use. The same MHMS was used at

2 keV ion detection energy. The IonCCD floating

potential setup was described in our previous work6.

The currently available readout time for the 2126

active pixels of the IonCCD (2.7 ms) limits the speed

of the IonCCD and more importantly decreases the

duty cycle of the detector (3.6% at 100 µs integration

time). Though such short integration times are never

used in direct detection mode, the use of an MCP will

call for shorter integration times (< 1 ms) to achieve

higher speeds.

Thus, the MCP’s high gain (104) will motivate either

the development of faster electronics to achieve the

currently available 2 kHz maximum chip operating

speed or a complete chip redesign to attain even

higher speeds.