Behaviour of Ma PMTs in Magnetic fields Introduction

Behaviour of Ma. PMTs in Magnetic fields Introduction What are Ma. PMTs ? Ma. PMTs and LHCb Motivation Why study the Effect of Magnetic field Experiment and Results Setup and Data Acquisition Two Types of Ma. PMTs Longitudinal/Transverse Magnetic Field Analysis Comparison Old vs New focusing Tube 9 C 20 A 2 – Anodes Behaviour Cause of the Losses Cross Talk over Adjacent Channels Solution Conclusion Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

What are Ma. PMTs ? ● Compact Multi anode Photomultipliers Tubes ● Convert light into electric signal with spatial resolution QE Wavelength Behaviour of Ma. PMTs in B fields Pixel Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● LHCb: Large Hadron Collider beauty experiment ● Detector being build at CERN for the study of CP violation Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● LHCb: Large Hadron Collider beauty experiment ● Detector being build at CERN for the study of CP violation ● 2 Photo detectors designs Ma. PMT HP D Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● LHCb: Large Hadron Collider beauty experiment ● Detector being build at CERN for the study of CP violation ● 2 Photo detectors designs Ma. PMT HP D Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● LHCb: Large Hadron Collider beauty experiment ● Detector being build at CERN for the study of CP violation ● 2 Photo detectors designs Ma. PMT HP D Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● LHCb: Large Hadron Collider beauty experiment ● Detector being build at CERN for the study of CP violation ● 2 Photo detectors designs Ma. PMT HP D Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Ma. PMTs and LHCb ● RICH (Ring Imaging CHerenkov detector) essential for charged particles identification Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004 Shield

Ma. PMTs and LHCb ● Example of a 3 x 3 Ma. PMT cluster with quartz lenses (testbeam data with ring reconstruction for over several thousands of events) Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Why study the Effect of Magnetic field ● RICH 1 is next to magnet with a 4 Tm-1 Field ● Used to be a shield but removed to increase the path bending to improve triggering. ● Field in RICH 1 region 40 m. T ➢ ● Field inside RICH 1 2. 5 m. T ➢ Old LHCb Design Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Setup and Data Acquisition ● A magnet : Field from (+/-) 0 - 35 m. T ● Ma. PMT in a light tight box ● Light source: 4 LED ring l ● High voltage: -1 k. V ● APVm readout system Behaviour of Ma. PMTs in B fields = 430 nm Longitudinal axis Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Two Types of Ma. PMTs 9 C series: Old focusing Behaviour of Ma. PMTs in B fields 9 K series: New focusing Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Longitudinal Magnetic Field Longitudinal field in z-direction 90% Ma. PMT resists fields up to 2 m. T Normalised light yield in whole Ma. PMT Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Transverse Magnetic Field Transverse field in xdirection 90% Ma. PMT insensitive to transverse fields up to 20 m. T (200 G) without shielding Normalised light yield in whole Ma. PMT Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Comparison Old vs New focusing Longitudinal field in zdirection New focusing more sensitive to the field by ~ 10 -20% Normalised light yield in whole Ma. PMT Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Tube 9 C 20 A 2 - Anodes Behaviour – zdirection Colour Conclusion Legend 1 m. T 2 m. T 3 m. T 4 m. T 5 m. T 6 m. T 7 m. T 8 m. T 9 m. T 10 m. T 15 m. T 20 m. T 25 m. T 30 m. T 35 m. T “Negative” field ● Behaviour of Ma. PMTs in B fields Top and bottom row drop first 5 th row population drops while side rows increases ● ● ~50% lost for edge rows at 3 m. T Column population decreases uniformly ● Same behaviour for tube 9 K 20 C 3 (new) Distribution example at 6 m. T ● Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Tube 9 C 20 A 2 - Anodes Behaviour – zdirection Colour Conclusion Legend 1 m. T 2 m. T 3 m. T 4 m. T 5 m. T 6 m. T 7 m. T 8 m. T 9 m. T 10 m. T 15 m. T 20 m. T 25 m. T 30 m. T 35 m. T “Negative” field ● Behaviour of Ma. PMTs in B fields Top and bottom row drop first 5 th row population drops while side rows increases ● ● ~50% lost for edge rows at 3 m. T Column population decreases uniformly ● Same behaviour for tube 9 K 20 C 3 (new) Distribution example at 6 m. T ● Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Cause of the Losses Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Longitudinal field Cross Talk over Adjacent Channels Row 4 against row 5 Conclusion: No Cross talk induced by magnetic field ● Field m. T Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Row 4 against row 5 Transverse field Longitudinal field Cross Talk over Adjacent Channels Conclusion: No Cross talk induced by magnetic field ● Field m. T Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Solution: Shielding with mu-metal Old focusing ZOOM-IN � -metal shield: 0. 9 mm thick 13 or 20 mm extension Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004

Conclusions Behaviour of Ma. PMTs in B fields Reinhardt CHAMONAL – Iop Birmingham April 5 -7 2004