Performance of B-sensor types EUDET NIKHEF VS F. Bergsma 12/9/2007

ATLAS fixed T mapper T CMS fixed T Used by mapper T LHCb mapper T ALICE mapper T MICE T Results on performance : “Final results on B-sensor calibration” F. Bergsma, ATLAS Magnetic Field Workshop, CERN “Measurement of the solenoid magnetic field” M. Aleksa et. al, ATL-MAGNET-PUB If calibrated at Tesla and deg. C: Δ |B| 1 Gauss |B| ≤ 1.4 Tesla Δ angles 0.3 mrad 15 o C < T < 29 o C Δ orientation 1 mrad Some data on NIKHEF sensor

On page 17: Figure 12.1 shows the Bz normalisation correction that we use for the high field maps. There is no significant structure versus probe number. The mean is zero by construction and the r.m.s. is 3.4 ×10-4, slightly better than the ±10 G expectation. In the case of the low field map, the r.m.s. is 0.8 ×10-4 also slightly better than the ± 2 G expectation. calibration procedure of low field map the same as used in EUDET I was not involved in analysis !

0.37 T 1.14 T 1.4 T   +10 G |B| -5 G T +10 G |B| -5 G T 1 2 NIKHEF after one year NIKHEF Sensor

  0.37 T 1.14 T 1.4 T G |B| -5 G T +10 G |B| -5 G T NIKHEF after one year NIKHEF Sensor

0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 1 2 EUDET Temp from LT 1019 Immediat after cal.   EUDET Sensor old

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 1 2 EUDET Temp from LT 1019 After 8 days EUDET Sensor old

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 3 4 EUDET Temp from LT 1019 Immediat after cal. EUDET Sensor old

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 3 4 EUDET Temp from LT 1019 After 8 days EUDET Sensor old

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 1 2 EUDET Temp from DS60 Immediat after cal. EUDET Sensor new

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 1 2 EUDET Temp from DS60 After 6 days EUDET Sensor new

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 1 2 EUDET Temp from DS60 After 0.24 year EUDET Sensor new

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 3 4 EUDET Temp from DS60 Immediat after cal. EUDET Sensor new

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 3 4 EUDET Temp from DS60 After 6 days EUDET Sensor new

  0.37 T 1.14 T 1.4 T +10 G |B| -5 G T +10 G |B| -5 G T 3 4 EUDET Temp from DS60 After 0.24 years EUDET Sensor new

Very preliminar result from EUDET mapping in DESY: Comparing at symmetry plane through centre of Magnet Putting two different sensors on same place (|B 1 |-|B 2 |) / |B| = 1.2 ± 3.9 GAUSS on 12 X Tesla No correction for misalignment bench magnetic material etc.

Eric Heijne, chief of electronics department NIKHEF gave me the schematic of their B-sensor, under condition that we quote “NIKHEF” whenever we refer to it and that electronics which uses this schematic must carry the NIKHEF logo From where come these differences? We have to look at the schematics of the sensors

NIKHEF B-sensor diagram R11+C11, R10+C10 tested with 15 daisy chained sensors R21, R22 only needed if µP is not placed IC5 needed for level transfer Q1 mount on distance of the Hall-sensors against magnetic interference Short traces as possible against magnetostrictive effects Traces twisted against inductive effects Field tuning: R4=8k66*Bx/1.4, R13=374*Bx/1.4 Analogue, digital part and power have there own ground plane connected to each other on one place. Identifier has to be added to the µP or extra chip. A D P A A A A P A D D D P P A D DA D A D P A A A A P A D D D P P A D DA X

Strong points NIKHEF B-sensor 1 Hall current and reference voltage of the ADC are derived from the same voltage stabilizer. So in first order the variations in the voltage stabilizer are cancelled. No field dependent band-gap voltage reference is used. 2 The hall current is small, about 0.24 mA, so the probe dissipates little heat and the offset remains stable. 3 Due to the low hall current the voltage drop over the Hall probe is small, so this current can be put in series through all 3 probes, which means variations in the current would not affect the direction of the reconstructed field. If the voltage drop over the Hall probe becomes too big you run out of the common mode limits of the input amplifier and you have to use three independent current sources. 4 There is only one and very stable current source, made with an opamp and a FET. 5 In addition to 4 the Hall current is fed to a very high precision resistance and the voltage over this resistance is used to make a system gain calibration. So the sensitivity depends largely only on this one single precision resistance. 6 There is a high precision, standardized, thermistor in the circuit to measure the temperature of the Hall probes and a circuit which give the 0 degree and 100 degree reference for it. 7 Some shaping of the logic signals are done. 8 Addressing is done by a reprogrammable micro processor. Cards can be addressed one by one, but also have a common broadcast address to start a simultaneous measurement. New features can be easily added.

EUDET B-sensor diagram

mcp23s08 eudet ATtiny22L nikhef ds2405 new reliable ok test easy to program no jumpers yes software yes fixed Addr. 8byt flexible no yes change prog. no broadcast (listen all) +/- ++ +/- unique ID no yes small +/ not too slow + + test Addressing

If we want to have in short time a very good B-sensor: Use NIKHEF design = for the moment the best we have tested in many places over 2 years We can use their schematic and layout if we leave the NIKHEF logo on Robust B-sensor, well protected against many sorts of perturbations Good platform for further research, e.g. ≥ 10 Tesla sensor Addressing ? Some upgrade desirable Conclusions

Replace FET of current source by a less magnetic one or increase its distance from the Hall probes Some trajectories on the pcb can be shorter, reduce loops Design an intermediate board with an ERNI mini flat cable connector Optimize clock circuit Identifier Fixation hall probes easy mounting, more stability Replacement Hall probe KSY44 HGT2100 has changed NIKHEF is coming with an upgrade too, maybe we do a joint effort? Upgrades NIKHEF sensor