The Research on Anti-Interference Techniques in AMS-C Power System

Congyan Chena,Zhuang Xionga, Jianqing Lia, Qiao Menga, Qing Xiaa.

aAMS Research Center, Southeast University,Si Pai Lou 2#,Nanjing, 210096, China

AMS-C system is the ground version of AMS-01 system, which is composed of Silicon Tracker detector (TRK),Time of Flight detector (ToF) and Magnet. The total system is finished in March 2005, and installed in June2005. However, static inductance, source hi-frequency pulse, source harmonic noise and strong electric magneticinterference influence strongly the electronic devices of AMS-C in our test process. Some basic principles of thegood grounding, shielding and power distribution practices are applied to limit peak or surge interference. Thenisolation transformer and filter are considered as an ulterior step to increase the capability of anti-interference.By these composite measures, the anti-interference ability of system is improved and the operation requirementreached. The improved system now can collect favorable particle events and reach anticipant purpose. The firstbatch of data collected by the AMS-C system has been sent to our overseas AMS partner research institutionsand has proven effective and reliable.

1. AMS-C System

Alpha Magnetic Spectrometer (AMS) is a par-ticle physics detector in space. The purpose isto perform accurate, high statistics, long dura-tion measurements of energetic primary chargedcosmic ray spectra in space [1,2]. The AMS-Csystem (AMS-China system) is a modified ver-sion of AMS-01 system, realized by INFN of Italy,Geneva University, MIT and Southeast Univer-sity [3]. The system is a turnkey magnetic spec-trometer consisting of Silicon Tracker detector(TRK), Time of Flight detector (ToF) and Per-manent Magnet, flown on Space Shuttle Discov-ery (STS-91) in space for 10 days. The magnetwas made from 64 high-grade Nd-Fe-B sectors.AMS-C silicon tracker detector has 24 double-sided silicon ladders. After refurbishment, thesilicon ladders were placed onto 4 planes of a newsupport structure, which was inserted into thepermanent magnet of AMS01. And then 3 lay-ers of ToF counters (2 up and 1 down) coveredthe magnet free bore, as shown in figure 1.

The system can measure the Rigidity (p/Z) ofthe particle by the Tracker from the deflection ofthe trajectory, Velocity and Direction from theToF, and Charge Magnitude taken by the dE/dxmeasurement in the Scintillators and Tracker.From above, the sign of the charge and particle

ToF

Magnet

TRK

Figure 1. The configuration of AMS-C.

mass are derived. The AMS-C system can notonly provide technological support, diagnose er-rors in the system and set up a data processingnetwork for the upcoming AMS-02 experiment,but also do broad scientific experiments, and belikely to get some original fruits. On the otherhand, the original data of charged high-energyparticle acquired by AMS-C system on earth sur-face can provide most valuable source materialfor our space science. Through this system, wewill not only discover new physical performanceof outer-space particles on earth surface but also

Nuclear Physics B (Proc. Suppl.) 166 (2007) 249–251

0920-5632/$ – see front matter © 2007 Elsevier B.V. All rights reserved.

www.elsevierphysics.com

doi:10.1016/j.nuclphysbps.2006.12.018

hi-frequency common noise in powerline is

TRK

detector

ToF

detector Isolation

transformer

UPS Filter

VME

crate

NIM

crateComputer

Figure 2. AMS-C Power wiring.

develop outer space exploration technologies.The total system had finished in March 2005,

and installed in June 2005 in Southeast Uni-versity. However, the commissioning of AMS-Csystem is not as our wishes. In our test pro-cess, static inductance, high voltage flashover,hi-frequency pulse, source harmonic noise andstrong electric magnetic interference bring unpre-dictable but unneeded effects to the electronic de-vices of AMS-C. To satisfy the requirement of op-eration, we apply some basic principles [4–6], suchas good grounding, shielding and isolation trans-former. And these measures will be discussed inthe next section.

2. Commissioning and Improvement of

Power Supply

All the electronic parts of system were testedin INFN of Italy before shipping. However, inthe electronic devices of such scale and complex-ity as AMS-C system, we must pay enough care-ful attention to the implementation of ground-ing, shielding and power distribution when in-stalling and commissioning in ourselves Univer-sity. The noise sources of powerline mainly comefrom common ground wire and high-harmonic in-terference. In order to improve the operation ofelectric equipments in AMS-C system, we takesome measures as follows:

2.1. Shielding of the common ground wire

The electronic equipments of AMS-C systemmainly divide into five parts: TRK detector, ToFdetector, VME crate, NIM crate and computercontrol part. Since the data collected from twodetectors must be processed in the same trig-ger system and DAQ system, and not all of thedata paths are implemented via optical links (inAMS-C system, only the path from VME crate tocontrol computer is via optical link), the groundcontact among five parts except computer is ab-solutely needed. To minimize accidental groundloops, we also connect the ground wires with cop-per conductor to support structures to excludethe unpredictable connection.

2.2. Suppression of powerline noise with

isolation transformer

Isolation transformer

Isolation transformer plays an important rolein solving power noise problem. It is generallyconstructed with a primary and secondary wind-ing closely wrapped about the same ferrous core.As noise pulses come, the reactance caused bythe capacitance between the windings tends toshunt them, and limit high frequency part. Sincecommon-mode noise is referenced to the powersystem ground, the most obvious method to elim-inate it is by grounding the transformer center tap

C. Chen et al. / Nuclear Physics B (Proc. Suppl.) 166 (2007) 249–251250

to the system ground via the lowest impedancepath possible. However, the power of isolationtransformer must be enough.

Filter

Another valid measure to eliminate hi-frequency common noise in powerline is addinga filter in front of power input end. Due to χC =1/(ωC) (where C is a bypass capacitance) andχL = ωL, when hi-frequency signal coming, thecascaded inductance will generate great impen-dence, and then the amplitude is evidently elimi-nated. More, the bypass capacitance can performa function of short-circuit for hi-frequency signal.The configuration of isolation transformer and fil-ter are illustrated in figure 2.

2.3. Other measures

1. Earth line. The resistance between twomain distributors (metallic frame) is notmore than 2 Ohm in AMS-C system.

2. UPS. In order to protect the AMS-C sys-tem when power supply shuts down sud-denly, we place UPS equipment before iso-lation transformer and filter. The power ofUPS is 8kw.

3. Source segregate. The power source for de-tector electronic equipments should be sep-arated from that for other things (cranes,lights, etc.).

3. Conclusion

By applying isolation transformer, filter, andcomposite measures, the operation of AMS-C sys-tem is improved, and the debugging and commis-sioning works were finished in September 2005.The first batch of data collected by the AMS-Csystem has been sent to overseas AMS partnerresearch institutions and has proven effective andreliable.

However, there are many things else to do forAMS-C system. One thing is to make the systemas perfect or effective as possible. Some of thephysics researching goals of AMS-C system aredark matter, antimatter and cosmic ray studies,

partly belonging to total AMS experiment. Thisis a long duration and hard work.

Acknowledgements

We gratefully acknowledge many colleagues ofINFN of Italy, Geneva University, and MIT whohave greatly supported our work.

This work has been supported by Hi-Techresearch and development program of China(2004AA306H10).

REFERENCES

1. J. Alcaraz et al.. Search for antihelium in cos-mic rays. Phys. Lett B461:387-396, 1999.

2. M. Aguilar et al.. The Alpha magneticspectrometer (AMS) on the internationalspace station, part I, results from the testflight on the space shuttle. Physics Reports,vol.366(6): 331-404, 2002.

3. http://ams.pg.infn.it/amsc/.4. Bruce C. Gabrielson and Mark J. Reimold,

Suppression of powerline noise with isola-tion transformers. EMC EXPO87, 1987, SanDiego, CA.

5. N. Bondar, B. Bylsma, S. Lusin, A.Madorsky, P. Robl, V. Sedov. CMS EMUCSC policy on grounding, shielding andpower distribution.

6. Tao Xiaoping, Wang Guicheng. Study ofanti-interference technique in klystron gallery.Proceeding of the 2001 particle acceleratorconference, Chicago.

C. Chen et al. / Nuclear Physics B (Proc. Suppl.) 166 (2007) 249–251 251