A Possible New Approach to Positron
Emission Tomography Using Time of
Flight from Multi-Gap Resistive Plate
Chambers to Replace or Enhance the Use
of Inorganic Crystals
Bernard Liu
Manhasset High School
200 Memorial Place
Manhasset, NY 11030
Bernard Liu
Acknowledgements
All research was carried out independently, this past summer at Brookhaven
National Laboratory, under the guidance and support of faculty mentors, Dr. Timothy
Hallman and Dr. Lijuan Ruan. Research consisted of acquiring data via simulation runs
in C++ and GEANT. Collaboration with researchers at Tsinghua University and the
University of Science and Technology of China for possible experimental data is also
underway.
Abstract
Current detectors utilized in PET scans consist of an inorganic crystal, referred to
as a scintillator, and a photo-multiplier tube. The system is not efficient and is also very
costly to produce; a small crystal 1cm in size can cost more than $100. Inorganic crystals
take time to grow and when ready, are relatively small, indicating that a PET detector is
both expensive and only covers specific areas. Therefore the purpose of this experiment
is to utilize MRPC-TOF technology to design a new detector for use in PET. MRPCs are
much cheaper to produce and as a result can be used for larger, full body PET scans. The
design calls for a total of 20 gas gaps. Glass plates will be replaced by a semiconductive
glass which will reduce resistivity and increase efficiency. Calculations predict that an
MRPC with 20 gas gaps, semiconductive glass plates 3cm thick, under ~1.2kV/mm
electric field will have 99.99% photon conversion efficiency, a maximum of 30%
electron penetration probability, and close to 95% detection probability. This will have an
actual efficiency ranging from 70-90%, where a 30% is sufficient. Experimental data
from an MRPC workshop at Tsinghua University will be further analyzed.
2
Bernard Liu
Introduction
MRPCs, otherwise known as Multi-gap Resistive Plate Chambers, are detectors
currently in use in high-energy physics experiments, such as the Solenoidal Tracker at
RHIC (STAR). The MRPC is essentially a multi-layered detector, where its vital area
consists of the middle layers composed of glass plates, which are held electronically
floating. In between these glass plates is a gaseous mixture, usually a heavy, dense gas
such as Freon or Xenon. (Ruan, 2004) When a charged particle traverses the MRPC, it
will ionize in the gas gaps creating an electron cloud. This electron cloud will then follow
the avalanche process and induce a charge on a set of readout pads on the other side of
the MRPC. (Ruan, 2004) This technique is being looked at to replace current PET
(Positron Emission Tomography) detectors, which are both costly and relatively small in
size, while the reduced cost of the MRPC can lead to the development of larger detectors.
The goal of this experiment is to design a new method of photon detection which
increases precision and efficiency of current detectors. The possibility of using MRPCTime Of Flight technology to replace the current PMT/Scintillator system is being
currently studied. Important issues to take into account are the MRPC’s vulnerability to
“background noise”, which leads to accidental coincidences. Also, scattered photons may
also change direction and energy, further complicating the detection process.
The first few MRPCs were developed in China at Tsinghua University, led by Dr.
Yi Wang. He developed the basic structure for the MRPC which was then utilized in
ALICE (A Large Ion Collider Experiment) at CERN (European Organization for Nuclear
Research). At STAR, a similar detector system was needed to test for charged particles.
At first the PMT and Scintillator system was proposed for use, but due to its high cost, an
alternative was needed. Wang’s MRPC was then utilized in STAR. It was much more
cost-effective, being ten times cheaper than previous detectors. (Wang, 2009)
The MRPC is made of many layers including an outer “honeycomb” layer for
structural purposes, a electrical readout printed circuit board (PCB), an insulting Mylar
layer, an outer glass layer (often referred to as the electrode), a thin carbon layer after,
and then a series of thinner, inner glass layers separating multiple gas gaps (filled with a
gaseous mix, in STAR-TOF this gas mixture is made up of Freon 134a and Iso-butane),
which then is followed by an additional outer glass layer. The figure below show the
3
Bernard Liu
structural makeup of MRPCs used in STAR. (Ruan, 2004)
Figure 1 shows the structure of the MRPCs used at STAR with two side views, the top being the
view lengthwise and the bottom being the view widthwise. (Ruan, 2004)
These MRPCs are arranged around a central point where a particle collision
would take place, whether this is be from a positron-electron annihilation or two gold
ions colliding into each other at relativistic speeds. (Badawi , 1999) In both instances,
particles are emitted from the collision and are picked up by the MRPC, which will give a
readout on the particle’s time of flight. In PET, two photons with 511 keV (given that
they do not lose energy via Compton scattering) will be produced and picked up by the
MRPC detector. (Einsberg and Resnick, 1985) In PET, this pair of photons will hit a
series of scintillators, or inorganic crystals, which will create multiple low energy
photons from the incident photon. These photons are then all directed to the Photomultiplier tube (PMT) where metal plates are aligned at slanted angles; these are called
dynodes. The photons will then all hit the dynodes, going through the photoelectric effect
and creating many electrons, which multiply in number due to both an increased number
of photon conversions and the avalanche process. Eventually the electron charge is
amplified and creates a voltage, which is then used to make a final readout for the
incident photon. (Vaska, 2006) On the exact opposite side, the same process occurs with
the other photon from the photon pair produced, and if the two photons are registered
within a specific time frame, they are considered a coincidence event. The positron
annihilation event is then localized by tracing back along the line of coincidence (also
known as line of response or LOR) to show the level of activity in the certain region. The
4
Bernard Liu
higher the level of activity, the more likely it is that the area is causing harm; for example
cancerous cells frequently catabolize excess glucose, a sign of increased chemical
activity. The scanner is in essence only a photon counter and has a time window of about
1 nanosecond. (Vaska, 2006)
The emitted particles, when in an MRPC, behave a bit differently. They will
traverse the outer layers and once in the gas gaps go through the avalanche process,
which creates an exponentially growing number of charged particles (though pair
production/ annihilation) called a shower. (Blanco et. al., 2004) The avalanche process,
sometimes known as an electron cascade, is a form of electric current multiplication in
that it can greatly increase the number of free electrons. This usually occurs only in
strong electric fields. STAR's TOF uses a potential difference of 7000 volts. When the
avalanche process begins, free electrons are accelerated by the electric field to very high
speeds. These high-speed electrons will move through the gas gaps and strike the atoms,
which will knock off free electrons, going through the ionization process. The original
electron and the newly freed one are both accelerated and both strike other atoms,
knocking even more electrons free. This process continues until the current reaches a
maximum and creates an electron shower. However, if this process continues for too
long, the process enters streamer mode where there are too many free electrons and the
number of electrons is simply too high for the MRPC to detect, at a point above the
MRPC’s rate capability. If the photons exceed the rate capability of the MPRC, the
efficiency is drastically reduced. (Blanco et. al., 2004)
This electron shower, created in the gas gaps, will then travel to the other side and
be picked up by a set of copper readout strips, which will send an analog signal the PCB.
This in turn will send a digital signal readout to a computer, which can be used to identify
the particle and its time of flight. To reduce the amount of “noise” or unwanted signals, a
threshold is applied to remove a part of the signal that is vulnerable to noise. A threshold
is an applied lower limit to the readout. However, one problem arises as the pads lose
accuracy and are less precise when they are too large, which is further complicated by
cross talk, or when the signal for one pad is read by another pad. (Wang, 2009)
The MRPCs measure the exact time of flight that a photon has taken and when
another photon is detected on an MRPC on an opposite side, within a specified time
5
Bernard Liu
period, (known as the time frame) such as 80 picoseconds, it is considered a coincidence
event and the two photons can be assumed to have come from the same collision. The
paths are then traced back along the LOR, identifying the exact point of impact, helping
to create an image of the object, or in the case of PET, identifying the area with the most
chemical activity. (Fonte et al., 2000) This technique could be used to identify the time of
flight of a photon, however the photons will likely not ionize in the gas gaps so extra
steps must be taken help convert the photons to charged particles, most probably
electrons, so that the particles can ionize in the gas gaps and create a signal readout for
the PCB.
Further work by Dr. Yi Wang in 2009 researched replacing the glass plates with a
semiconductive glass. This new type of glass plate had a greater attenuation coefficient
and rate capability when compared with the regular glass plates. He found that as the
voltage (electric field) was increased, the efficiency generally increased, and the time
resolution was sharply lowered, with time resolution being how precise the time
measurement is; having a lower time resolution meant having a more precise instrument.
Other findings show that at increasing counting rates of incoming photons, efficiency
stayed relatively constant until a sharp drop at about 30 kHz/cm2 but time resolution
steadily increased. The most ideal counting rate was therefore deemed to be 28 kHz/cm2
where the efficiency was high and the time resolution was still below 100 picoseconds.
(Wang, 2009)
Figure 2 shows the MRPC’s efficiency versus its rate capability, which can reach up to 28kHz/cm 3, while
still keeping the time resolution below 100ps. (Wang, 2009)
STAR’s MRPC work was based off the MRPC of Wang. Some specifications
6
Bernard Liu
include glass with 1012-1013 .cm resistivity, carbon tape with 100,000 , six gas gaps at
0.22 mm each, gas gaps filled with a mixture of 95% Freon-134a and 5% iso-butane, time
resolution of 80 picoseconds, and an above 90% efficiency. Early results also showed the
extent of the MRPC’s noise rate and avalanche signal ratio. The noise rate was very low,
averaging around 13 Hz with one outlier at about 54 Hz. The avalanche signal ratio was
generally very high with an average at about 95%, with a minimum at 80%. The average
time resolution of the prototype MRPC was also recorded to be around 100 picoseconds,
which was very good for an early detector. (Wang, 2009)
Also noted was that the lowered resistivity of the electrodes (glass plates)
increased the neutralization of charge on the glass. This sped up the recovery of the
electric field in the gas gap, which aided in increasing the rate capability of the MRPC.
Based off this conclusion, Wang implemented a new semiconductive glass in his
prototype. His results showed that the semiconductive glass could sustain higher counting
rates of incoming photons as compared to the Schott glass (high quality German glass)
previously used. One last notable finding was that as particle rate was increased, the time
resolution would increase, without much effect on the efficiency. (Wang, 2009)
Figure 3 shows the rate capability of the semiconductive glass versus the average Schott glass. The
semiconductive glass can afford higher particle rates by far. (Wang, 2009)
7
Bernard Liu
Figure 4 shows the efficiency and time resolution versus the particle rate in the MRPC. The type of gas
mixture used in the gas gaps is also shown. (Wang, 2009)
At ALICE in CERN, a prototype MRPC was also created for use in their
detectors. They went with a stacked MRPC design, which provided more structural
support and reduced the need for higher voltages as a lower voltage could maintain an
equally high electric field. The figure below shows the structure of the stacked MRPC. It
is simply two MRPCs placed on top of each other, sharing one electrode which will act as
the anode and the two outer glass layers acting as cathodes. (ALICE Collaboration,
2002.)
Figure 5 shows the cross section of a double stacked MRPC versus a single stack, both of which have 6 gas
gaps. (ALICE Collaboration, 2002.)
Findings showed a precise MRPC with a great time resolution. Only 0.06% of
8
Bernard Liu
photons did not fall in the 500 picosecond time frame and only 1.21% of photons did not
fall within the 250 picosecond time frame. The efficiency was also very high for both the
10-gap and 6-gap MRPC created (both stacked so two 3 gas gap MRPCs stacked and two
5 gas gap MRPCs stacked together), once enough voltage was applied. Further findings
showed that efficiency was much better with a dual stack MRPC then with a single stack
of just 6 gas gaps. Also important to note is that a lower electric field was needed to reach
a higher efficiency with the stacked MRPC design but once past 120 kV/cm, streamer
mode was activated, which sharply reduces efficiency. The MRPCs in use at ALICE
however had a lower rate capability than Wang’s MRPC with sharply reduced efficiency
at around 900 kHz/cm2. (ALICE Collaboration, 2002.)
Figure 6 shows the efficiency of three MRPC strips (two double stack and one single stack) versus the
electric field. With the stacked MRPC, a lower electric field is needed for a higher efficiency.
(ALICE collaboration, 2002)
Figure 7 shows efficiency of two MRPC strips versus particle rate. (ALICE collaboration, 2002)
Other experiments showed more ways to increase MRPC efficiency. Belli et. al.,
2006, experimented with electrode thickness and found that with increased thickness,
9
Bernard Liu
efficiency rose; however, it is important to note that voltage had to be increased for that
effect to be achieved.
A study by Blanco et. al. in 2004 experimented with an entirely new design for a
MRPC, where 20 or more gas gaps were utilized. Multiple MRPCs were stacked on top
of each other to create a large MRPC having a very large number of gaps. Efficiency
higher than 98% was reached but the design was significantly modified. In between each
electrode (glass plate) metal plates were inserted and a readout was taken from each gas
gap. These readouts were then all combined to show the final result. Not much is known
about this sole MRPC prototype besides its high efficiency and its overall design, but it
seems to be a viable alternative. If its details were revealed, perhaps some of its methods
could also be integrated into the proposed MRPC prototype.
Figure 8 shows the MRPC efficiency using electrodes 0.4 mm and 1mm thick. The efficiency reaches up to
98%, almost reaching 100%. (Belli et al., 2006)
Therefore the purpose of this experiment is to design a new method of photon detection
which increases precision and efficiency of current detectors using MPRCs to replace the
current PMT/Scintillator system.
Methods and Materials
Preliminary Calculations
Calculations, simulation data, and archival data were used for basic analysis of
materials and calculations of efficiency; however this method was not completely
accurate due to randomization of particles. First, calculations were used to find the
energy loss (dE/dx) of the various materials using the material’s electron stopping power
(in MeV cm2/ g). This information was taken from ESTAR, run by the National Institute
of Standards and Technology. Afterwards, attenuation coefficients were then used to
10
Bernard Liu
calculate the intensity of photons after passing through a certain material, using the BeerLambert Law, If=Ie-t, with If as the final intensity of the photons, I as the initial intensity,
 as the material's attenuation coefficient, and t as the material's thickness. This was then
used to calculate the photon conversion efficiency, or what percent of photons could have
gone through the material, most importantly the photon conversion efficiency in the glass
plates.
Simulation Runs
A C++ program was utilized for simulation of the detector system. A few
parameters for the program were inputted and a few efficiency readouts were given. One
problem with the C++ simulation is that it is a very conservative prediction and gives the
lower limit of the range of efficiencies, so it is quite inaccurate. It also only accounts for
one ionization process in the gas gaps when in fact there could be more, maybe even
three, which would drastically increase efficiency and signal amplitude. Another defect
of this program is that it has difficulty taking into account multiple stacks of MRPCs and
new types of glass plates, the two main improvements utilized.
A simulation run using GEANT, with a Monte Carlo simulation, was used for
more accurate data, replacing the C++ runs. The program was exclusively used by a
graduate student at USTC (University of Science and Technology of China) and data
relied on his accurate trials. The Monte Carlo simulation was much more accurate than
the C++ program and successfully incorporated all parameters of the proposed detector.
The Monte Carlo data successfully showed the probability of the electron penetrating the
glass.
Electron Detection Efficiency
STAR Archival data was used to calculate the electron detection efficiency in the
gas gaps. These readings were acceptable replacements for data from PET detectors since
once the electron reaches the gas gap, it will ionize without depending on the incident
particle. The three main parts of the detection process were the photon conversion
efficiency (taken from calculations), the possibility of the electrons penetrating the glass
and reaching the gas gap (taken from Monte Carlo simulation), and the probability of the
detection of the electron in the gas gaps (taken from STAR archival data). These readings
help determine the final efficiency of the entire detector system.
11
Bernard Liu
Results
To calculate final efficiency of photon detection for this system, a three-part
method was used. The first part was the photon conversion efficiency, which was
obtained through the use of Beer-Lambert law and attenuation coefficients of the various
materials in the MRPC. The second step was to find the possibility of the electrons
penetrating the glass which was found using data from C++ simulation runs and the
GEANT (Monte Carlo) simulation from USTC graduate student Tien-Xiang Chen.
Results are shown below. The third and final step was to find the probability that the
electron produced, once in the gas gaps, would be detected on the readout pads. All three
steps must be successful in order for the photon to be detected, since all are needed to
produce a signal to be detected.
Calculations (in appendix) show that a MRPC with 20 gas gaps and with 3 cm
thick semiconductive glass plates would have a photon efficiency of >99.99%. The
“standard” MRPC, with 6 gas gaps and soda-lime glass 540 microns thick, only had a
photon conversion efficiency of 14.67%, showing improvement with the addition of
semiconductive glass. However the greatest improvement came with the increased
number of gas gaps, which greatly helped as it provided more material for the photon to
traverse.
C++ simulations show that efficiency is relatively high for the 6 gas gap MRPCs,
but not for the 20 gas gap MRPCs, which may be because the electron will not have
enough energy to traverse the multiple layers. The chart below shows the thickness of
electrodes, the type of glass, and the number of gas gaps and their effect on the efficiency
of the MRPC based on C++ simulation trials. The 6 gas gap MRPCs has an efficiency
that levels off quickly after 1 cm at about 30%. This chart accounts for the probability
that the electron will penetrate the glass layers and enter the gas gap, one part of
determining its efficiency.
12
Bernard Liu
Figure 9 shows the C++ simulation efficiencies. The 6 gas gap MRPC has the highest efficiency at about
30%, which levels off very quickly once the electrodes were thicker than 1 cm. (STAR Archives, 2009)
Monte Carlo simulations done by PhD Tien-Xiang Chen have shown that a
MRPC with PCB 1.5mm thick, copper tape 0.05mm thick, graphite film 0.12mm thick,
an outer glass layer 0.7mm thick, and an inner glass layer 0.4mm thick would have a
relatively low percentage of electrons entering the gas gaps themselves, and a similarly
low probability for the electrons to ionize and create an electron cascade. The chart below
shows the effect of the number of gas gaps versus the efficiency, in a much more mature
simulation using the Monte Carlo simulation though GEANT. In this case, as the gas
gaps increase, efficiency increases because there is a higher likelihood that the electron
will ionize and go through the avalanche process. It is important to note that the highest
efficiency reached is only about 30% for a 20 gas gap MRPC, where 30% of electrons
will enter the gas gap ionize to create a charge. Again, this chart accounts for the
probability that the electron will enter the gas gap.
13
Bernard Liu
Figure 10 shows the GEANT simulation efficiency. Efficiency increased as the number of gas gaps
increased. (STAR Archives, 2009)
Figure 11 shows the electron detection efficiency for particles in STAR. (STAR Archives, 2009)
Through selected archival data from more than 10,000,000+ runs in STAR
showed that the electron detection efficiency ranged from just under 60% to about 96%,
averaging at about 85%. Also interesting to note is that the time resolution of the detector
is relatively high. Final resolution of the system can be calculated as Tres2 = 12 + 22 or
117ps2 = 90ps2 + (ToF)2, where the resolution of the Time-of-Flight detector was 74.7596
ps.
Although the efficiency for two parts of the detection process, the photon
14
Bernard Liu
conversion efficiency and the electron detection efficiency, are relatively high (99% and
85%), the electron penetration possibility is relatively low. Further optimization should
focus on this one part of the process, perhaps by using different materials or different
thickness of the glass.
The final efficiency is still affected by the possibility that the electron produced
will create a charge, through induction, on the readout pads. This efficiency is much
lower and has been calculated to be about 66% for a six, 0.54 mm, gas gap MRPC with
Soda-lime glass, based off limited trials of C++ and Monte Carlo simulation. This
efficiency is usually very high, meaning that most of the time the electron charge will be
captured on the readout pads, and since the simulation program only reports the lowest
possible efficiency; the actual efficiency is probably much higher. For the proposed
design, the efficiency can reach 85-90%. That probability is good enough for use in PET
and the time resolution also matches with standard detectors.
Discussion
The purpose of this experiment was to design a cost-effective and more efficient
method of photon detection for use in PET using MRPCs. Currently, the most viable
method to increase efficiency is to increase the gas gaps, which would increase photon to
electron conversion and the number of ionization processes in the gas gaps. The idea,
based off simulations run by Belli et al. (2006), called for a MRPC for detecting photons,
but used 20 gas gaps to increase the efficiency up to almost 90 percent (where about 30
percent would be sufficient for PET scans). Numerous calculations (in appendix) were
then done to test the effects of increased gas gaps and different glass types (Soda-lime,
Borosilicate glass, and Lead Glass) on the efficiency of photon conversion. It was found
that once more gas gaps were included, the photon conversion efficiency shot up, usually
about 30 percent. In this project's proposed idea, the gas gaps would be increased, but
also the type of glass (currently just soda-lime glass) would be changed to a
semiconductive glass used at Tsinghua University (who were among the groups who
created STAR's MRPCs). This glass has a very low resistivity as compared to the other
glass types (1010  compared to 1013  for regular glass), increasing rate capability, or
the amount of photons that the detector can handle, and increasing time resolution.
15
Bernard Liu
Decreasing the resistivity of the glass also affects the rate capability, or the rate of the
photons that the detector can handle without losing efficiency (to about 20 kHz/cm2).
Other factors this glass would help include the time resolution and the overall efficiency
of the detector.
Structural problems then arose including how to keep the electric field the same
without increasing the voltage too drastically. A simple solution of stacking two MRPCs
was suggested, which would lower the required voltage, yet still keep the number of gas
gaps the same. In the stacked MRPC, the initial electron will traverse the entire MRPC
and go through the avalanche process while all the electrons generated by the avalanche
process will be forced into the middle plate due to the electric field and contribute to the
charge. In addition, this method would also produce larger signal amplitude, better time
resolution, and be much more structurally stable because a problem with having too many
gas gaps with no support is that the glass plates may warp when under high voltage,
shown below. To further these improvements, more stacks with fewer gas gaps could be
used. This both drastically lowers the required voltage for the electric field and also
increases efficiency. However, with an increased number of MRPC stacks, electrons will
have difficulty traversing the increased amounts of material, so individual readout strips
should be placed between each gas gap, such as in the MRPC used by Blanco et. al., and
then the signals combined for a final readout. This is currently not a major concern within
the scope of this project and should be looked into in future studies. Another problem
with this is that the output signal amplitude will also be much lower. This could be
resolved by lowering the threshold, but this in turn increases background noise.
Figure 13 shows the warping of the glass plates when under high voltage. (ALICE collaboration, 2002)
The performance of this proposed MRPC has yet to be tested experimentally, but based
off of simulation trials and efficiency calculations; it is a viable replacement for the
16
Bernard Liu
current inorganic crystal detectors used for PET.
The final design of the MRPC includes the following few additions to the current
model MRPC (taken from STAR). First the glass plates will be replaced by
semiconductive glass, which is made up of SiO2, BaO, Fe2O3, SrO, V2O5, and Na2O.
These plates were thicker, from an initial thickness of 1.1 mm to 3 cm. Then these
MRPCs had the number of gas gaps decreased to only two. Ten of these MRPCs were
layered on top of each other to create a multi-stack MRPC with a final gas gap count of
twenty gas gaps.
Conclusion
The current most ideal design for a prototype MRPC for use in PET uses many of
the methods listed above. Efficiency will increase when the number of gas gaps is
increased to 20 gas gaps (by having 10 sets of 2 gas gap MRPCs stacked together) and
when the 0.54 mm inner and 1.1 mm outer glass plates are replaced with 3 mm thick
semiconductive glass plates. This MRPC is to be put under a ~1.2kV/mm electric field
for the most optimal reading. Current calculations predict that this detector has a photon
conversion efficiency higher than 99% and a final detection efficiency of ranging from
70-90%. Optimization should still go into using a thinner glass so that the electron will be
able to enter the gas gaps, but still have the glass thick enough so that the photons can
convert into electrons, as the probability that the electron enters the gas gap is still
relatively low.
Future Studies
To further this project, a more mature and thorough Monte Carlo simulation trial
will be run in GEANT, which will be used to more accurately calculate efficiency. The
simulations however are only predictions and not completely accurate. Experimental
results will be included; however, this data must be done by the manufacturers of the
MRPCs. A model of the MRPC-PET proof of principle prototype will be created at
Tsinghua University as part of their current MRPC workshop and the researchers there
are willing to build a model MRPC for this project. They are currently testing its
efficiencies with a gamma producing machine and will share the data as soon as
17
Bernard Liu
experimentation is done. Currently, the scientists are building a prototype MRPC and
hope to have data before the end of the year. Data analysis using a package of analysis
tool called HBOOK is currently being utilized in preparation for archival data from an
MRPC chamber exposed to a radioactive source at one of the collaborating Chinese
Universities.
Further data is still in the process of being obtained and analyzed. Using the
experimental results, specialized engineering and structural problems will also be shown,
which then can be fixed. From there more specific characteristics of the MRPC can be
improved, such as time resolution and elimination of cross talk between readout pads.
Experimental data will be utilized for verification of information and further data
analysis.
Appendix
Photon Efficiency of
MRPC
Type of Glass
Gaps
Semi-conductive Glass
6
0.2147634839
0.1478177695
0.2336921268
0.892191415
0.987253283
0.998492896
20
0.3992176848
0.3484423774
0.4524197441
0.998547877
0.999997600
0.999999996
6
0.1467914436
0.1405687980
0.1585322691
0.659843270
0.873103455
0.952660842
20
0.2629040684
0.2347477808
0.2937720819
0.954387832
0.997631939
0.999877057
6
0.1501490010
0.1434734675
0.1623937787
0.678517389
0.886653886
0.960037211
20
0.2702457908
0.2407629513
0.3025487244
0.961495102
0.998312424
0.999926038
6
0.1810204738
0.1701866419
0.1976514994
0.810422484
0.960584656
0.991805097
20
0.3358070463
0.2948677787
0.3795246532
0.992104057
0.999929036
0.999999362
Soda-Lime Glass
Borosilicate Glass
Lead Glass
0.054 cm
.04 cm
.07 cm
1.0 cm
2.0 cm
3.0 cm
Table B shows the actual photon efficiency of the MRPC, with all the different types of glass and number of gas gaps
listed. Photon efficiency reaches above 99.99%, but an important thing to note is that the electron efficiency may not be
that high. Currently it is around 70%.
18
Bernard Liu
Selected Bibliography
ALICE Collaboration. Addendum to the Technical Design Report of the Time of
Flight System (TOF). CERN. 2002.
Badawi, Ramsey. Introduction to PET Physics-Positron Emission Tomography in
Medical Imaging. 1999.
Belli, G. et al. RPC: from High Energy Physics to Positron Emission
Tomography. Journal of Physics: Conference Series 41. Pg. 555-560. 2006.
Bichsel, H. et al. 27. Passage of Particles Through Matter. PDG. Page 2-33. July
28, 2008.
Blanco, A. et al. An RPC-PET prototype with high spatial resolution. Nuclear
Instruments and Methods in Physics Research A. Vol. 533 Pg. 139-143. 2004.
Blanco, A. et al. Development of large area and of position-sensitive timing
RPCs. Nuclear Instruments and Methods in Physics Research A. Vol. 478 Pg. 170-175.
2002.
Blanco, A. et al. Efficiency of RPC Detectors for Whole-Body Human TOF-PET.
Nuclear Instruments and Methods in Physics Research A. Vol. 602. Pg. 780-783. 2009.
Blanco, A. et al. RPC-PET: A New Very High Resolution PET Technology.
IEEE Explore. Pg 2356- 2360. 2004.
Blanco, A. et al. Spatial Resolution on a Small Animal RPC-PET Prototype
Operating Under Magnetic Field. Nuclear Physics B. Vol. 158. Pg. 157-160. 2006.
Blanco, A. et al. Very High Position Resolution Gamma Imaging with Resistive
Plate Chambers. Nuclear Instruments and Methods in Physics Research A. Vol. 567. Pg.
96-99. 2006.
Coucerio, M. Sensitivity assessment of wide Axial Field of View PET systems via
Monte Carlo simulations of NEMA-like measurements. Nuclear Instruments and
Methods in Physics Research A. Vol. 580 Pg. 485-488. 2007.
Coucerio, M. RPC-PET: Status and Perspectives. Nuclear Instruments and
Methods in Physics Research A. Vol. 580 Pg. 915-918. 2007.
Fonte, P. et al. A new high-resolution TOF technology. Nuclear Instruments and
Methods in Physics Research A. Vol. 443. Pg. 201-204. 2000.
Fonte, P. et al. High-resolution RPCs for large TOF systems. Nuclear Instruments
19
Bernard Liu
and Methods in Physics Research A. Vol. 449. Pg. 295-301. 2000.
Fonte, P. and V. Peskov. High-resolution TOF with RPCs. Nuclear Instruments
and Methods in Physics Research A. Vol. 477. Pg. 17-22. 2002.
Fonte, P. High-Resolution timing of MIPs with RPCs – a model. Nuclear
Instruments and Methods in Physics Research A. Vol. 456. Pg. 6-10. 2000.
Einsberg, Robert and Robert Resnick. Quantum Physics of Atoms, Molecules,
Solids, Nuclei and Particles. “Photons-Particlelike Properties of Radiation” Pg. 31-60.
Wiley, University of Michigan. 1985.
NIST (National Institute of Standards and Technology). ESTAR- Stopping Power
and Range Tables for Electrons.
Ruan, Lijuan. Pion, Kaon, Proton and Antiproton Spectra in d+Au and p+p
Collisions at snn= 100 GeV at the Relativistic Heavy Ion Collider. University of Science
and Technology of China. Sept. 2004.
Vaska, Paul. Physics & Instrumentation in Positron Emission Tomography.
Center for Translational Neuroscience at Brookhaven National Laboratory. July 21,
2006.
Wang, Yi. A prototype of a high rating MRPC. Chinese Physics C. Vol. 33, No.
5, Pg. 374-377. May 5, 2009.
Wang, Yi. MRPC Construction Status in Tsinghua. Department of Engineering
Physics, Tsinghua University. April 27, 2009.
Wang, Yi. Study on the performance of high rating MRPC. Nuclear Instruments
and Methods n Physics Research A. Vol. 536, Pg. 425-430. 2009.
20