Heavy Scintillating Glasses for Future High Energy Particle Physics Experiments
Chun JiangSchool of Electronic
Information and Electrical EngineeringShanghai Jiao Tong University
Tianchi ZhaoUniversity of Washigton
Nov. 6, 2007
Prototype Stack30 x 30 cm steel absorber plates, 2 cm thick
for a 1 cm gap between steel plates
CALICE Analog Hadron Calorimeter for ILC
Active detector: Plastic scintillator tiles5 cm x 5 cm, 0.5 cm thick
Light collected by Wavelength Shifting FibersReadout by Silicon photomultipliers
Average density of the CALICEanalog calorimeter is ~5.5 g/cm3
Hadron Calorimeter
MPPC
MPPC
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MPPC
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GLD Calorimeter Design Examples
Electromagnetic Calorimeter
Tungsten, lead or steel absorber plates
plastic scintillator tiles or strips
Our Proposal
To replace the structure of metal and plastic scintilaltor plates by scintillating glass blocks that glued together to form homogeneous modules. It will be - A total absorption calorimeter for optimum resolution
- Can combine the functions of EM and Hadron Colorimeters
A total absorption hadron calorimeter can have excellent energy resolution because it provide several ways to measure energies required to break up nuclei, which is mostly “invisible” in a sampling hadron calorimeter since such energy is mostly absorbed by the inactive metal plates.
Two OptionsOption 1:A conventional scintillation calorimeter that reads the scintillation light only
Hadron energy that is invisible in a sampling calorimeter can be recovered by observing ionization energies from heavy nuclei fragments, spallation protons, ’s released by fast neutron inelastic scatterings and recoiling nuclei due to fast neutron elastic scatterings, and energies released by thermalized neutrons captured by the calorimeter media
Option 2:A dual readout calorimeter that reads the scintillation light and cherenkov light separately. Compensation for the invisible energy can be achieved by this method.
See the reference
http://ilcagenda.linearcollider.org/contributionDisplay.py?contribId=202&session
Id=45&confId=1556
Excellent Hadron Energy Resolution
Fluka Study by A. Ferrari and P.R. Sala of INFN-Milan for a total absorption calorimeter with four different materials presented in calor2000 Integration time
Energy resolution
A total absorption hadron calorimeters can potentially achieve excellent energy resolution for both EM and hadron showers
Note: It is important to choose the right calorimeter media so that fast neutrons can be absorbed quickly (< ~1 s) and locally and contribute to the energy measurements
Calorimeter Technologies for HEP
Historically, only electromagnetic calorimeters are total absorption calorimeters for high energy physics experiments.
Hadron calorimeters are sampling calorimeters made of heavy metal absorber plates and active detector layers with very small energy sampling ratio (typically <<10%)
A total absorption calorimeter was proposal for the D-zero detector at Fermi National Lab based on scintillating glass bars in the 1980’s. But that proposal was not adopted.
Developing an appropriate scintillation material is the key for a total absorption calorimeter to become reality
Basic RequirementsCalorimeter total volume : on the order of 100 m3
• High density
• Short radiation length
• Short interaction length
• Scintillation light properties compatible with the
readout method
ATLAS hadron calorimeter CMS hadron calorimeter
Scintillating Glasses as a Calorimeter Media for High Energy Physics
• Scintillating glass is inexpensive compared to crystal scintillators
• Light yield is normally less than 1% of NaI
• light yield of scintillating glass can be several times higher
than the light yield of PbWO4 crystal used by CMS experiment
Scintillating Glasses SCG1-C
• Scintillating glass: SCG1-C with modest density was developed
in early 1980’s by Ohara Optical Glass Company in Japan
Major components: BaO 44% and SiO2 42% with 1.5% Ce2O3
• It is easy to fabricated and have good scintillation properties
• SCG1-C glass was considered for the EM and hadron calorimeter
of the D-zero experiment at Fermilab in the 1980’s, but was not
adopted
• SCG1-C was used in several HEP experiments as EM calorimeters
• Density 3.5 g/cm3 is too low for our purpose
• No thermal neutron isotopes, not good for hadron calorimeters
Fluorohafnate Scintillating Glasses
• Attempts were made to develop Fluorohafnate Scintillating
Glasses for CMS EM calorimeter by CERN’s Crystal Clear
Collaboration in the 1990’s
(HfF4-BaF2-CeF3) + (5% Ce2O3 doping)
• Density is quite high 5.95 g/cm3
• Low scintillation light yield ~0.5% NaI in near UV region
• Expensive and very difficult to make into sufficiently large size
• No thermal neutron isotopes, not good for hadron calorimeters
• Not good for our purpose
B2O3-SiO2-Gd2O3-BaO 30:25:30:15
doped with Ce2O3 or other dopantsChun Jiang, QingJi Zeng, Fuxi Gan,Scintillation luminescence of cerium-doped
borosilicate glass containing rare-earth oxide, Proceedings of SPIE, Volume 4141, November 2000, pp. 316-323
• Density 5.4 g/cm3 is sufficient for an ILC calorimeter
• Contains a large amount of thermal neutron isotopes
boron and gadolinium
• Will capture thermalized neutrons in a short time and in close proximity to hadron showers providing a mean for recovering invisible energies in hadron showers
Our Proposed BSGB Scintillating Glass
BSGB Glass
Density 5 - 5.5 g/cm3
Light yield ~500 ’s/MeV (?)
Decay time 60 - 80 ns
Scintillation wavelength 460 nm
Radiation length 1.8 cm
Interaction length 20 - 25 cm (estimate)
Some Properties of the BSGB Glass
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Transmission Spectrum of GSGB Glass
A: Base glass without dopingB: GSGB glass with 5%Ce C: After radiation
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Fluorescence Spectrum of GSGB:Ce Glass
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BSGB Glass
Scintillation Light Yield (80 keV X-ray excitation)
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Manufacturing Issues of Gadolinium Oxide Glasses
1. Conventional melting method with resistance furnace, reduction agents or reduction gases
2. Cost: Gd2O3 is more expensive than PbO, Bi2O3, Ce2O3, La2O3, etc, but cheaper than Yb2O3, Lu2O3, Ga2O3, GeO2, TeO2, etc.
3. Large block of Gd2O3 based scintillation glass with density of over 5.0g/cm3 can be fabricated.
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Future Plans (1)
• Make samples for testing by Fermilab (Dr. A. Para),
University of Washington and Italian groups
5 cm x 5 cm and 10 cm x 10 cm, 1 cm to 2 cm thick
• If successful, supply ~ 20 liters of glass blocks for a
EM calorimeter module to be tested in the beam
at Fermilab
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Future Plan (2) Scintillating Glass for a Dual Readout Calorimeter
• Investigate different doping for BSGB glass
- The Ce+3 doping is used to general fast short wavelength
scintillation light that is not necessary for an ILC calorimeter.
- Ce+3 doping must be made in a reducing atmosphere and is
difficult to control
- Longer and slower scintillation light is required for a dual
readout caloriemter
• For dual read design (readout scintillation and Cherenkov light
separately) , the scintillating glass must have
Scintillation light spectrum peak > ~500 nm
and/or
Scintillation light decay time > ~100 ns
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Future Plans (3)
• Investigate PbO-Bi2O3 scintillating glass
with high density of over 6.0-7.0g/cm3 and high transmission at shorter wavelength.
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• The BSGB scintillating glasses with Ce2O3 is an excellent
candidates for total absorption calorimeters for colliders
at very high energies that can achieve good EM and hadron energy
resolution
• Further studies are necessary to make samples for testing
• BSGB scintillating glass with different doping with improved
properties and suitable for the dual readout calorimeter can be
developed
Conclusions