Performance of a spaghetti calorimeter prototype with tungsten absorber and garnet crystal fibres

A spaghetti calorimeter (SPACAL) prototype with scintillating crystal fibres was assembled and tested with electron beams of energy from 1 to 5 GeV. The prototype comprised radiation-hard Cerium-doped Gd<math display="inline" id="d1e435" altimg="si1.svg"><msub><mrow/><mrow><mn>3</mn></mrow></msub></math>Al<math display="inline" id="d1e443" altimg="si2.svg"><msub><mrow/><mrow><mn>2</mn></mrow></msub></math>Ga<math display="inline" id="d1e451" altimg="si1.svg"><msub><mrow/><mrow><mn>3</mn></mrow></msub></math>O12 (GAGG:Ce) and Y<math display="inline" id="d1e463" altimg="si1.svg"><msub><mrow/><mrow><mn>3</mn></mrow></msub></math>Al<math display="inline" id="d1e471" altimg="si5.svg"><msub><mrow/><mrow><mn>5</mn></mrow></msub></math>O12 (YAG:Ce) embedded in a pure tungsten absorber. The energy resolution was studied as a function of the incidence angle of the beam and found to be of the order of <math display="inline" id="d1e482" altimg="si6.svg"><mrow><mn>10</mn><mtext>%</mtext><mo>/</mo><msqrt><mrow><mi>E</mi></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">⊕</mo><mn>1</mn><mtext>%</mtext></mrow></math>, in line with the LHCb Shashlik technology. The time resolution was measured with metal channel dynode photomultipliers placed in contact with the fibres or coupled via a light guide, additionally testing an optical tape to glue the components. Time resolution of a few tens of picosecond was achieved for all the energies reaching down to (18.5 <math display="inline" id="d1e503" altimg="si33.svg"><mo>±</mo></math> 0.2) ps at 5 GeV.