Heavy Scintillating Glasses for Future High Energy Particle Physics Experiments Chun Jiang School of Electronic Information and Electrical Engineering Shanghai Jiao Tong University Tianchi Zhao University of Washigton Nov. 6, 2007

Prototype Stack 30 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 tiles 5 cm x 5 cm, 0.5 cm thick Light collected by Wavelength Shifting Fibers Readout by Silicon photomultipliers Average density of the CALICE analog calorimeter is ~5.5 g/cm 3

Hadron Calorimeter 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 Options Option 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 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 Requirements Calorimeter total volume : on the order of 100 m 3 High density Short radiation length Short interaction length Scintillation light properties compatible with the readout method ATLAS hadron calorimeterCMS 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 PbWO 4 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 SiO 2 42% with 1.5% Ce 2 O 3 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/cm 3 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 (HfF 4 -BaF 2 -CeF 3 ) + (5% Ce 2 O 3 doping) Density is quite high 5.95 g/cm 3 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

B 2 O 3 -SiO 2 -Gd 2 O 3 -BaO 30:25:30:15 doped with Ce 2 O 3 or other dopants Chun JiangChun Jiang, QingJi Zeng, Fuxi Gan, Scintillation luminescence of cerium-doped borosilicate glass containing rare-earth oxide, Proceedings of SPIE, Volume 4141, November 2000, pp QingJi ZengFuxi Gan Density 5.4 g/cm 3 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 g/cm 3 Light yield ~500  ’s/MeV (?) Decay time ns Scintillation wavelength460 nm Radiation length1.8 cm Interaction length cm (estimate) Some Properties of the BSGB Glass

14 Transmission Spectrum of GSGB Glass A: Base glass without doping B: 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: Gd 2 O 3 is more expensive than PbO, Bi 2 O 3, Ce 2 O 3, La 2 O 3, etc, but cheaper than Yb 2 O 3, Lu 2 O 3, Ga 2 O 3, GeO 2, TeO 2, etc. 3. Large block of Gd 2 O 3 based scintillation glass with density of over 5.0g/cm 3 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-Bi 2 O 3 scintillating glass with high density of over g/cm 3 and high transmission at shorter wavelength.

21 The BSGB scintillating glasses with Ce 2 O 3 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