We report on the performance of a micro-hole and strip plate, fabricated with standard gas electron multiplier-production procedures, presenting 40-[mu]m hole-diameter and 30-[mu]m wide anode strips. Multiplication factors of 5Ã—104 were reached in an Ar/Xe (95/5) atmosphere at about 1Â bar; the energy resolution is of the order of 14% (FWHM) for 5.9-keV X-rays.http://www.sciencedirect.com/science/article/B6TJM-4BRJY00-1/1/d80a918485bf806c1feae6bbd514d4e

Veloso, J. F. C. A.

Maia, J. M.

Requicha Ferreira, L. F.

Santos, J. M. F. dos

Breskin, A.

Chechik, R.

Oliveira, Rui de

College of Education and Professional Studies Curriculum Committee

The Keep

Eastern Illinois University
The Keep
Curriculum Committee Administration & Publications
1998
December 14, 1998
College of Education and Professional Studies Curriculum Committee
Follow this and additional works at: http://thekeep.eiu.edu/ceps_curriculum
This Article is brought to you for free and open access by the Administration & Publications at The Keep. It has been accepted for inclusion in
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Recommended Citation
College of Education and Professional Studies Curriculum Committee, "December 14, 1998" (1998). Curriculum Committee. 46.
http://thekeep.eiu.edu/ceps_curriculum/46
r ' /} College of Education and Professional Studies 
Curriculum Committee Minutes 
December 14, 1998 
Present: Rebecca Cook (SPE); Marietta Deming (HST); Mary Greenlaw (STG); Pat 
Hartzler, Student Representative (LST); Dean Hitch; Kevin Hussey (PED); Janet 
Lambert (EC/ELE/MLE); Roger Luft (BED); Judith Lyles (CSD) ; Jenelle Morris, 
Student Representative (PED); Don Smith (SED); Jeannie Walters, Charleston 
Public Schools; John Weber (LST); Bonnie Wilson 
Absent: Karina Elmoznino, Student Representative (CSD); Tamara Engnell, Student 
Representative (SPE); Larry Janes (EDA) 
Mary Greenlaw called the meeting to order. 
The minutes from the November 9, 1998, meeting were approved. 
Marietta Deming presented a proposal to remove the exclusion for Physical 
Education and Leisure Studies (Recreation Administration) majors from taking 
senior seminars EIU 4002C, Controversial Issues in the Health Care Industries, 
and EIU 4047C, Health Communication Issues. Following discussion, this 
proposal was approved. 
The meeting dates for the Spring, 1999, semester were discussed. The approved 
meeting dates are as follows: 1/25/99, 2/22/99, 3/22/99, and 4/26/99. The 
meeting time will remain at 2:30-3:30 p.m. 
The meeting was adjourned at 2:50p.m. 
Respectfully submitted, 
Bonnie Wilson 
-· ·-·. -.---.----~-~......q 
******************************* 
SPRING 1999 MEETING SCHEDULE 
January 25, 1999 
February 22, 1999 
March 22, 1999 
April 26, 1999 
2:30-3:30 Schahrer Room 
******************************* 
·. i • ..-, ~2 ~~- l 
.; 
DEC I 71998 


English

December 14, 1998

Eastern Illinois University

Eastern Illinois UniversityThe KeepCurriculum Committee Administration & Publications1998December 14, 1998College of Education and Professional Studies Curriculum CommitteeFollow this and additional works at: http://thekeep.eiu.edu/ceps_curriculumThis Article is brought to you for free and open access by the Administration & Publications at The Keep. It has been accepted for inclusion inCurriculum Committee by an authorized administrator of The Keep. For more information, please contact tabruns@eiu.edu.Recommended CitationCollege of Education and Professional Studies Curriculum Committee, "December 14, 1998" (1998). Curriculum Committee. 46.http://thekeep.eiu.edu/ceps_curriculum/46r ' /} College of Education and Professional Studies Curriculum Committee Minutes December 14, 1998 Present: Rebecca Cook (SPE); Marietta Deming (HST); Mary Greenlaw (STG); Pat Hartzler, Student Representative (LST); Dean Hitch; Kevin Hussey (PED); Janet Lambert (EC/ELE/MLE); Roger Luft (BED); Judith Lyles (CSD) ; Jenelle Morris, Student Representative (PED); Don Smith (SED); Jeannie Walters, Charleston Public Schools; John Weber (LST); Bonnie Wilson Absent: Karina Elmoznino, Student Representative (CSD); Tamara Engnell, Student Representative (SPE); Larry Janes (EDA) Mary Greenlaw called the meeting to order. The minutes from the November 9, 1998, meeting were approved. Marietta Deming presented a proposal to remove the exclusion for Physical Education and Leisure Studies (Recreation Administration) majors from taking senior seminars EIU 4002C, Controversial Issues in the Health Care Industries, and EIU 4047C, Health Communication Issues. Following discussion, this proposal was approved. The meeting dates for the Spring, 1999, semester were discussed. The approved meeting dates are as follows: 1/25/99, 2/22/99, 3/22/99, and 4/26/99. The meeting time will remain at 2:30-3:30 p.m. The meeting was adjourned at 2:50p.m. Respectfully submitted, Bonnie Wilson -· ·-·. -.---.----~-~......q ******************************* SPRING 1999 MEETING SCHEDULE January 25, 1999 February 22, 1999 March 22, 1999 April 26, 1999 2:30-3:30 Schahrer Room ******************************* ·. i • ..-, ~2 ~~- l .; DEC I 71998 

Estudo Geral

ARTICLE IN PRESSNuclear Instruments and Methods in Physics Research A 524 (2004) 124–129*Corresp
Coimbra, P
667; fax: +
E-mail a
1On leav
Beira Inter
0168-9002/$
doi:10.1016Recent advances in X-ray detection with micro-hole
and strip plate detector
J.F.C.A. Velosoa,b,*, J.M. Maiac,1, L.F. Requicha Ferreiraa,d, J.M.F. dos Santosa,
A. Breskinc, R. Chechikc, Rui de Oliveirae
aPhysics Department, University of Coimbra, P-3004-516 Coimbra, Portugal
bPhysics Department, University of Aveiro, P-3810-193 Aveiro, Portugal
cDepartment of Particle Physics, The Weizmann Institute of Science, 76100 Rehovot, Israel
dPhysics Department, University of Beira Interior, P-6201-001 Covilh *a, Portugal
eCERN 1211 Geneve 23 EST/DEM/PMT, Switzerland
Received 5 January 2004; accepted 7 January 2004
Abstract
We report on the performance of a micro-hole and strip plate, fabricated with standard gas electron multiplier-
production procedures, presenting 40-mm hole-diameter and 30-mm wide anode strips. Multiplication factors of 5 104
were reached in an Ar/Xe (95/5) atmosphere at about 1 bar; the energy resolution is of the order of 14% (FWHM) for
5.9-keV X-rays.
r 2004 Elsevier B.V. All rights reserved.
PACS: 29.40.n; 29.40.Cs; 85.60.Gz
Keywords: Microstrip gas counter; Gas electron multiplier; Micro-hole & strip plate1. Introduction
The introduction of the gas electron multiplier
(GEM) [1] prompted a new generation of radiation
gas detectors with a wide range of applications.
The GEM is an array of sub-millimetre holes,
etched through a thin polymer substrate, with
conductors deposited on each side. The avalanche
process occurs within the holes under the intenseonding author. Physics Department, University of
-3004-516 Coimbra, Portugal. Tel.: +351-239-410-
351-239-829-158.
ddress: jveloso@gian.ﬁs.uc.pt (J.F.C.A. Veloso).
e from University of Coimbra and University of
ior, Portugal.
- see front matter r 2004 Elsevier B.V. All rights reserve
/j.nima.2004.01.057electric ﬁeld established by a suitable potential
difference between the two surface electrodes.
Gains exceeding 103 are achieved with a single
GEM; higher gains can be obtained by cascading
several GEMs or by coupling GEMs with other
gaseous electron multipliers. It was demonstrated
that a micro-strip gas counter (MSGC) [2]
preceded by a GEM has higher gain and stability
compared to the MSGC alone [3]. Localization
can be obtained in GEM detectors by coupling
a properly patterned readout anode to a GEM [4].
Very high multiplication factors, exceeding 106–107,
have been measured with single photoelectrons in
gas-avalanche photomultipliers combining a
photocathode and cascaded GEM structures [5].d.
ARTICLE IN PRESS
J.F.C.A. Veloso et al. / Nuclear Instruments and Methods in Physics Research A 524 (2004) 124–129 125The lack of photon-feedback permitted high-gain
operation also in noble-gas mixtures, including
Ar–Xe [5].
The micro-hole and strip plate (MHSP) [6–9] is
a new micro-patterned structure, shown in Fig. 1.
It combines the features of both GEM and MSGC
in a single double-sided micro-structure: a con-Fig. 1. Photomicrographs of the MHSP used in this work: (a)
top-side and (b) micro-strip bottom-side.tinuous top-electrode and an MSGC-like struc-
tured bottom face. It provides two successive
independent charge-ampliﬁcation stages: electrons
are preampliﬁed within the GEM-like holes and
the resulting avalanche electrons are further multi-
plied on the bottom strips. The holes are aligned
within the cathode strips, while the anode strips
run between them. The special shape of the anode-
strip ends and the cathode electrode shape around
them was designed to prevent discharges. Similarly
to the GEM, an electric ﬁeld is established within
the holes through a potential difference, Vhole;
between the top-electrode and the cathode strips;
the potential difference, Vac; between the anode
and cathode strips, establishes an MSGC-like
electric ﬁeld on the bottom part of the MHSP.
With this design, the voltages between the top-
electrode and the cathodes, and between the
cathodes and the anodes, can be maintained well
below their breakdown threshold, while achieving
total gas gains similar, or even higher, than those
obtained with a single GEM or MSGC [9]. An
important additional advantage of this design is
the signiﬁcant reduction of photon feedback
and avalanche-ion back-ﬂow, discussed in detail
in Refs. [10–12]. The multiplication properties
of MHSPs and of cascaded multi-GEM and
MHSP have been systematically investigated in
Refs. [9,12].
Similarly to GEMs, the MHSP can be fabri-
cated using ﬂexible printed circuit board (PCB)
technology. However, the MHSP characteristics
are still limited by their manufacturing imperfec-
tions, resulting in a low production yield. In the
present work, we report on the performance of an
MHSP, chosen for its better quality, investigated
with soft X-rays, in atmospheric Ar–5% Xe gas
mixture. In particular, we discuss detector gain,
energy resolution and minimum detectable X-ray
energy.2. Experimental set-up and description
A schematic view of the MHSP principle of
operation is depicted in Fig. 2. The MHSP active
area is 2.8 2.8 cm2. The kapton and the copper
ﬁlm-thicknesses are 50 and 5 mm, respectively. The
ARTICLE IN PRESS
Fig. 2. Schematic of the MHSP-based detector.
J.F.C.A. Veloso et al. / Nuclear Instruments and Methods in Physics Research A 524 (2004) 124–129126micro-strip anode and cathode widths are 30 and
100 mm, respectively, with a 200-mm pitch. The
anode–cathode gap is 35 mm. The MHSP holes are
bi-conical, of diameters 40 mm in the kapton and
70 mm in the copper ﬁlm; they are arranged in an
asymmetric hexagonal lattice of 140- and 200-mm
pitch in the directions parallel and perpendicular
to the strips, respectively. The MHSP, enclosed
between two stainless-steel meshes, is assembled in
a stainless-steel vessel. The absorption/drift region
and the charge induction region are 3-mm wide.
Most soft X-rays interact in the absorption/drift
region above the MHSP, and the resulting primary
electron cloud drifts along the ﬁeld lines towards
the MHSP holes. The electrons undergo charge
multiplication in the holes; the avalanche-electrons
emerge on the other side of the MHSP, where they
are directed towards the anode strips and further
multiplied in the high anode-strips ﬁeld. For these
events, double-stage multiplication occurs. A small
fraction of X-rays may be absorbed in the
induction region below the MHSP, depositing
electron clouds that experience charge multiplica-
tion only at the anode strips, and resulting in much
smaller amplitude pulses. The gain of the MHSP
holes can be derived from the relative peak
positions of the two event types. The detector
was ﬁlled with an Ar–5% Xe mixture at 1.07 bar,continuously puriﬁed through getters [SAES
St172/HI/7–6/150C] at 150C, and maintained in
circulation by convection. This gas mixture is
known to be a Penning mixture, providing high
gain at relatively low voltages [5,8]; it is simple to
purify and has no ageing problems.
All electrodes were independently polarized.
The electrode of the induction region was
grounded; the drift electrode mesh was operated
at negative voltage, to ensure insensitivity to X-ray
interactions above the mesh. The cathode strips
voltage was kept constant throughout this work,
at 30V (induction ﬁeld of B100V/cm). The
electric ﬁeld in the drift region was kept constant
at B50V/cm. In order avoid damaging of the
MHSP; the bias voltages used in this study were
always kept below the micro-discharge onset.
Detector signals were fed through a Canberra
2006 preampliﬁer (sensitivity of 1.5V/pC) and a
Tennelec TC243 linear-ampliﬁer (4-ms shaping
time, 8-ms peaking time) to an EG&G 8096-
multichannel analyser. The electronic chain sensi-
tivity was calibrated for absolute gain determina-
tion, using a calibrated capacitor directly connected
to the preampliﬁer input and to a precision
pulse generator.
We used 5.9-keV X-rays from a 55Fe source,
ﬁltered through a chromium ﬁlm to remove the
6.4-keV Mn-Kb X-rays; for gain calibrations we
have also employed 22.1-keV Ag-Ka X-rays from
a 109Cd source, as discussed below. For peak-
amplitude and energy resolution determination,
pulse-height distributions were ﬁtted to a Gaussian
superimposed on a linear background.3. Experimental results and discussion
Fig. 3 presents the total gain of the MHSP and
the energy resolution as a function of Vac;
maintaining Vhole at 260V. The experimental data
reveal a characteristic exponential development of
the charge avalanche process in the proportional
regime. Total gains as high as 5 104 were
reached, about an order of magnitude higher than
those typically achieved with GEMs in Ar-hydro-
carbon gas mixtures [4,5,13]. The rather large
width of the present anode strips limits their
ARTICLE IN PRESS
1E+1
1E+2
1E+3
1E+4
1E+5
0 50 100 150 200 250 300
V ac (V)
Ab
so
lu
te
 g
ai
n
0
5
10
15
20
25
30
35
En
er
gy
 
re
so
lu
tio
n 
( %
 )
Vhole = 260 V
Fig. 3. MHSP total gain and detector energy resolution
(5.9-keV X-rays) as a function of Vac; for Vhole ¼ 260V, and
for Ar–5% Xe, 1 atm.
1E+0
1E+1
1E+2
1E+3
1E+4
1E+5
50 100 150 200 250 300
Vhole  (V)
Ab
so
lu
te
 g
ai
n
0
5
10
15
20
25
30
35
40
45
En
er
gy
 
R
es
ol
ut
io
n 
( %
 )
Vac = 260 V
Gtotal
Ghole
Fig. 4. MHSP total gain, holes gain and detector energy
resolution (5.9-keV X-rays) as a function of Vhole; for
Vac ¼ 260V, and for Ar–5% Xe, 1 atm.
Fig. 5. Typical pulse-height distribution for 5.9-keV X-rays
and Vac ¼ Vhole ¼ 260V, for Ar–5% Xe at 1 atm, acquired
during 50 h.
J.F.C.A. Veloso et al. / Nuclear Instruments and Methods in Physics Research A 524 (2004) 124–129 127electric ﬁeld strength; consequently, the maximum
achievable gain in this second ampliﬁcation stage
is limited to about 30. In principle, higher gains
should be attainable with thinner strips, as
demonstrated in Ref. [9]. The energy resolution
shown in Fig. 3 converges to a minimum value of
16% FWHM for Vac values above 130V; this is a
signiﬁcant improvement compared to the 23%
FWHM energy resolution recorded with MHSPs
of the previous generation [9].
Fig. 4 depicts the MHSP’s total gain, the holes
gain and the energy resolution, as a function ofVhole; maintaining Vac at 260V. The highest gains
recorded in the MHSP holes, of about 103, are
similar to those obtained with GEMs. The energy
resolution improves with increasing Vhole; conver-
ging to the minimum value of 16% for Vhole above
220V.
A typical pulse-height distribution obtained
with this detector for 5.9-keV X-rays is pre-
sented in Fig. 5, for Vhole ¼ Vac ¼ 260V. The
salient spectral features include the full-energy
absorption-peak from X-ray interactions in the
absorption/drift region, the Ar K-ﬂuorescence
escape-peak, the electronic-noise tail in the low-
energy end and a broad distribution under the
electronic-noise tail, which results from X-ray
interactions in the induction region. As shown in
Fig. 5, the low-energy limit due to the electronic-
noise tail is of the order of 10 channels. This
demonstrates the good prospects for the applica-
tion of this micro-structure to very soft X-ray
detection. Moreover, taking into account that the
mean energy to produce an electron–ion pair in
argon–xenon mixtures is about 22 eV, the use of
the MHSP for single-electron detection seems to
be a realistic possibility. Since the 5.9 keV X-ray
interactions on the induction region are not
completely separated from the electronic noise,
due to the low anode-strips gain, the gain of the
MHSP holes was obtained from pulse-height
spectra of 22.1-keV Ag-Ka X-rays (emitted from
a 109Cd X-ray radioactive source), by comparing
ARTICLE IN PRESS
0
100
200
300
400
500
600
700
800
0 200 400 600 800 1000
channel number
co
u
n
ts
 / 
ch
an
ne
5.9-keV X-rays
Ar escape-peak
RE =  14 %
Vac   = 210 V
Vhole = 250 V
Fig. 6. Typical pulse-height distribution for 5.9-keV X-rays, for
best energy resolution conditions Vac ¼ 210V and
Vhole ¼ 250V, and for Ar–5% Xe at 1 atm.
J.F.C.A. Veloso et al. / Nuclear Instruments and Methods in Physics Research A 524 (2004) 124–129128peak-heights from absorptions in the absorption/
drift region and in the induction region.
It is possible to further improve the detector’s
energy resolution, by better tuning the different
electrodes biasing. For example, energy resolu-
tions of about 14% FWHM was reached with
Vac ¼ 210V and Vhole ¼ 250V, as shown in Fig. 6.
Moreover, the detector can be made less sensitive
to X-ray interactions in the induction region, by
reducing its width and better tuning its electric
ﬁeld [8]. Note that the pulse-height distribution
presented in Fig. 5 was acquired throughout 50 h
and does not show signiﬁcant degradation in the
obtained energy resolution or electronic-noise tail,
when compared to pulse-height distributions
recorded over few minutes, e.g. Fig. 6.4. Summary and discussion
The experimental results obtained with this
MHSP conﬁrm a very stable operation, free of
spurious pulses and/or micro-discharges, and
without signiﬁcant drift in the detector’s pulse
amplitude. The present MHSP has 30-mm wide
anodes instead of the 10 mm of the previous MHSP
generation [9]; the thicker anodes result in lower
strip gain, about 30, but in a more stable MHSP
operation. It is expected, though, that future
MHSPs can be safely produced with 15–20-mm
wide anode strips, if required.Total gains around 5 104 were reached with
soft X-rays in a single MHSP structure operated
with atmospheric Ar–5% Xe. This gain, which
could be in principle further enhanced with thinner
anode strips, is about an order of magnitude
higher than the typical gain of a single GEM. In
the best operation conditions reached in this work,
an energy resolution of about 14% FWHM was
obtained with 5.9-keV X-rays.
The low-energy limit due to electronic-noise tail
is rather low, indicating good prospects for the
application of this micro-structure to soft X-rays
detection and possibly to that of single-electrons.
However, one should keep in mind that one could
precede the MHSP with a GEM or with a cascade
of GEMs; the latter would permit reaching higher
gains and more stable operation, with reduced ion
feedback [9,12].
2D charge imaging with the MHSP can be done
in different ways. For example, the anode strips can
provide one coordinate, while the other one could
be obtained by structuring the top MHSP face into
strips running orthogonally to the anode ones [6].
With suitable biasing voltages, the signal induced
on the top MHSP electrode can have as much as
50% of the anode-strip signal-height [14,15]. An
alternative approach is to obtain the second
coordinate, or both coordinates, from the positive
ions collected on the cathode plane coupled to the
MHSP at the induction region; this plane can be
structured and placed at close proximity, of several
hundred microns, from the MHSP [15].
The fact that the MHSP operates in a stable way
in Ar/Xe is of a prime importance. We presently
investigate Gas Proportional Scintillation Coun-
ters (GPSC) for X-ray spectroscopy and imaging,
where the scintillation light is detected in the same
gas volume with MHSP-based gas photomulti-
pliers with CsI photocathodes. The latter can be
reﬂective ones, deposited on the top face of the
MHSP or on that of a preceding GEM, as shown
in Ref. [16].Acknowledgements
Support is acknowledged to Funda@*ao para a
Ci#encia e a Tecnologia (FCT), Lisbon (under
ARTICLE IN PRESS
J.F.C.A. Veloso et al. / Nuclear Instruments and Methods in Physics Research A 524 (2004) 124–129 129POCTI and FEDER programs), through project
POCTI/FNU/49553/02 of the Instrumentation
Centre (unit 217/94), Physics Department, Uni-
versity of Coimbra, by the Israel Science Founda-
tion and by the Planning and Budgeting
Committee of the Council for Higher Education
in Israel. J.F.C.A. Veloso and J.M. Maia acknowl-
edge support grants from FCT. A. Breskin is the
Reuther Professor of Research in Peaceful use of
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