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

MPPCMPPC

MPPC

MPPC

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

14

Transmission Spectrum of GSGB Glass

A: Base glass without dopingB: GSGB glass with 5%Ce C: After radiation

15

Fluorescence Spectrum of GSGB:Ce Glass

16

BSGB Glass

Scintillation Light Yield (80 keV X-ray excitation)

17

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.

18

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

19

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

20

Future Plans (3)

• Investigate PbO-Bi2O3 scintillating glass

with high density of over 6.0-7.0g/cm3 and high transmission at shorter wavelength.

21

• 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