Materials for EM calorimeters
The energy resolution of a calorimeter RMS(E)/E is typically parametrized with a term
depending on the energy (called sometimes a stochastic term) a/Eb and
a constant term, added in quadratures. The power b is close to 1/2 for
sampling calorimeters, lead glass calorimeters etc. For materials with a very high
yield, like NaI, b is close to 1/4. In the table only the factor a
is shown. The constant term depends on the number of channels, calibration etc,
and for large calorimeters is about 1-2%.
Properties of the materials used for electro-magnetic calorimeters.
| Material |
Rad. length (cm) |
Nucl. length (cm) |
Molière R (cm) |
Ecrit, (MeV) |
Refrac. index |
Density (g/cm3) |
Decay const (ns) |
Peak emiss. (nm) |
Rel. light yield |
E resol GeV½ |
Rad. hardn. |
| TF1 glass | 2.74 | ? | 4.70 |
15 | 1.647 |
3.86 | Cher. | Cher. | 0.001 ? |
0.06 | 2 krad |
| NaI(Tl) | 2.59 | 41.4 | 4.50 |
? | 1.85 |
3.67 | 250 | 410 . | 1.0 |
0.02 | low |
| PbWO4 | 0.89 | 22.4 | 2.20 |
? | 2.30 |
8.28 | 5-15 | 420-440 | 0.01 |
0.034 | high |
| PbF2 | 0.93 | ? | 2.22 |
? | 1.82 |
7.77 | Cher. | Cher. | 0.001 |
0.06 | high |
Properties of several lead glasses
| Material |
Rad. length (cm) |
Nucl. coll. length (cm) |
Moliere R (cm) |
Ecrit, (MeV) |
Refrac. index |
Density (g/cm3) |
Pb weight % |
Rad. hardn. |
| TF1 | 2.74 | 56.6* | 4.70 |
15 | 1.647 |
3.86 | ? | low |
| F-2 | 3.06 | 22.7 ? | ? |
18.4 | 1.620 |
3.60 | 45 | ? |
| F8-00 | 3.1 | 22.5 | ? |
? | 1.620 |
3.60 | ? | ? |
| SF-2 | 2.76 | 21.8 ? | ? |
17.5 | 1.648 |
3.86 | 51 | ? |
| SF-5 | 2.54 | 21.4 ? | ? |
15.8 | 1.673 |
4.08 | 55 | ? |
| DF6c/SF6 | 1.70 | 17.8 ? | ? |
13.8 | 1.805 |
5.20 | 71 | ? |
| SF57 | 1.546 | ? | 2.61 |
12.4 | 1.89 |
5.51 | 70? | ? |
* - Nuclear interaction length (not the collision length)
Table 2. The chemical structure of lead-glass
| F8-00 | TF1-000 | TF101 |
| PbO | 45.0% | 51.2% | 51.2% |
| SiO2 | 42.8% | 41.3% | 41.5% |
| K2O | 10.4% | 7.0% | 7.0% |
| Na2O | 1.8% | — | — |
| As2O3 | — | 0.5% | — |
| CeO2 | — | — | 0.2% |
| Refractive index, ne | 1.62 | 1.65 | 1.65 |
E-Mail : gen@jlab.org
Last updated: Wed, 19 July 2001