1161 Enero, Electromagnetic Compatibility (EMC) and Noise Background Testing for DoubleChooz PMT System. Informes Técnicos Ciemat

Transcription

1 Informes Técnicos Ciemat 1161 Enero, 2009 Electromagnetic Compatibility (EMC) and Noise Background Testing for DoubleChooz PMT System J. R. Cepero F. J. Encabo Fernández I. Pepe A. Verdugo Departamento de Tecnología

2

3 Toda correspondencia en relación con este trabajo debe dirigirse al Servicio de Información y Documentación, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Ciudad Universitaria, MADRID, ESPAÑA. Las solicitudes de ejemplares deben dirigirse a este mismo Servicio. Los descriptores se han seleccionado del Thesauro del DOE para describir las materias que contiene este informe con vistas a su recuperación. La catalogación se ha hecho utilizando el documento DOE/TIC-4602 (Rev. 1) Descriptive Cataloguing On-Line, y la clasificación de acuerdo con el documento DOE/TIC.4584-R7 Subject Categories and Scope publicados por el Office of Scientific and Technical Information del Departamento de Energía de los Estados Unidos. Se autoriza la reproducción de los resúmenes analíticos que aparecen en esta publicación. Catálogo general de publicaciones oficiales Depósito Legal: M ISSN: NIPO: Editorial CIEMAT

4 CLASIFICACIÓN DOE Y DESCRIPTORES S72 electromagnetic interactions; noise; voltage regulators; testing; power supply; experimental data; spain; signals; electromagnetic fields

5 Electromagnetic Compatibility (EMC) and Noise Background Testing for DoubleChooz PMT System Cepero, J. R. (1) ; Encabo Fernández, F. J. (1) ; Pepe, I. (1)(2)(3) ; Verdugo, A. (1) 20 pp. 9 fig. 5 tablas Abstract: The DoubleChooz PMT system is a HV/signal splitter. In this report is presented an electromagnetic compatibility and background noise testing for the DoubleChooz PMT system. It was possible to proceed the EMC testing on different grounding configurations of PMT splitter due to its special PCB design, endowed of jumping points and a metal box ground electrode. Comprobación de Compatibilidad Electromagnética (EMC) y Ruido Ambiental para el Sistema PMT del Experimento DoubleChooz Cepero, J. R. (1) ; Encabo Fernández, F. J. (1) ; Pepe, I. (1)(2)(3) ; Verdugo, A. (1) 20 pp. 9 fig. 5 tablas Resumen: El sistema PMT para el experimento DoubleChooz es un separador HV/ señal. En este informe técnico presentamos las comprobaciones de compatibilidad electromagnética y de ruido electromagnético ambiental para el sistema PMT del experimento DoubleChooz. Ha sido posible ejecutar la comprobación EMC sobre diferentes configuraciones de puesta a tierra del separador PMT debido al especial diseño del circuito PCB, incluyendo puntos para puenteado y una caja metálica con un electrodo puesto a tierra. (1) Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Av. Complutense, Madrid, ESPAÑA. (2) Centro Brasileiro de Pesquisas Físicas (CBPF) Rio / BRAZIL. (3) Laboratorio de Propiedade Oticas IF Universidade Federal da Bahia / BRAZIL.

6

7 Electromagnetic Compatibility (EMC) and Noise Background Testing for DoubleChooz PMT system. J R Cepero 1, F J Encabo Fernadez 1, I. Pepe 1,2,3 and A Verdugo Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Av. Complutense, Madrid, SPAIN 2 Centro Brasileiro de Pesquisas Fisicas (CBPF) RIO / BRAZIL 3 Laboratorio de Propriedade Oticas IF Universidade Federal da Bahia / BRAZIL Introduction The DoubleChooz (DC) PMT circuit is composed at least by five distinct components. Figure 1 shows that schematics, where one can find the 24 channels high voltage VME power supply (A1535P CAEN), the high voltage distribution patch panel, the PMT HV/signal splitter, the PMT resistive base and the PMT cabling system. The PMT cabling system is composed by a set of four cables, the 52 wire plus shielding KERPEM high voltage multi core with RADIALL 691 connector coming from the VME +HV power supply to the distribution patch panel. Two meters of HCT high voltage cable, conform to the CERN safety rule IS23, connecting the distribution patch panel to the PMT splitter. The RG 303/U, 22 meters long, from the PMT splitter to the PMT resistive base. And finally, the RG58 signal cable (20 m), connecting the PMT HV/signal splitter to DChooz detection electronics. VME +HV power supply 1 HV distribution patch panel 2 PMT HV/signal splitter 3 PMT resistive base 4 Figure 1. The DoubleChooz PMT circuit schematics To DChooz detection electronics

8 Despite the fact that all cables are well shielded, is well known that a long cable line usually acts as an antenna, being a good input for pick up noise. Even if, most terminations are 50 Ohm, a first estimation seems to point out that the HV power supply internal impedance can be as high as 200 k Ohm, decreasing the whole system noise immunity. In this report is presented an electromagnetic compatibility and noise testing for the DC PMT system, the meaning of that is get information about what kind of noise immunity one can expect for one single PMT. The PMT High Voltage/Signal Splitter internal grounding configuration During the PMT splitter design process, different circuitry and printed circuit board (PCB) routings have been tried. Its testing version 1 allows several different grounding configurations dues to special PCB jumping points and the metal box ground electrode. In figure 2 is presented the PMT splitter over view (metal box (open), press cables, fixation screws and PCB). GND electrode BOX GND C1 R2 R1 R3 B LED1 C2 A R4 C GND electrode press cable inlet Figure 2. PMT splitter over view (metal box, press cables, fixation screws and PCB) In figure 2 the jumping points are named A, B and C, selecting their existence and the type of connection among them one can, in conjunction with the ground electrodes,

9 determine the grounding configuration of the PMT Splitter. See table 1. Another variable considered in the test process was the fact of being operating with the splitter metal box open (no covering plate) or box closed. Notice that the open box configuration is justified as a matter of test, in DoubleChooz operation, the cover of all splitters must be on for safety and humidity sake. Table 1. PMT Splitter grounding configuration. Jump A Jump B Metal box GND connected to PCB Metal box covering Connected Connected Connected Closed Connected Not Connected Not Connected Connected 100 Ohm resistance Connected / / Connected 100 Ohm resistance 100 Ohm resistance Not Connected Not Connected 100 Ohm resistance Obs: the C jump was kept always connected Not Connected Open In table 1 are presented 28 different testing situations, it's important stress that in operation these number is divided by 2, the metal box must be closed, as mentioned before.

10 The tests design Two different tests have been designed to the DChooz PMT system. In the first case, the local electromagnetic noise background (at CIEMAT MADRID) was used as signal source to determine the PMT system noise immunity. Figure 3 presents the experimental setup used for this testing. 220 k Ohm 22 m RG303/U cable 20 m RG58 cable DChooz Splitter PMT resistive base +HV PMT OUT ADVANTEST R3132 Spectrum Analyzer Figure 3. First testing or local electromagnetic noise background test (experimental setup). On that case, the noise inducted in the the whole PMT system is measured at once by the ADVANTEST R3132 spectrum analyzer. Different PMT splitter grounding configurations (see table 1) has been tried. Six frequency bands was selected, optimizing the test resolution and sensibility. Table 2 presents those frequency bands.

11 Table 2. First test frequency bands (scanning bands) Initial and final frequencies Band number 9 KHz 100 KHz B1 100 KHz 2 MHz B2 1 MHz 10 MHz B3 10 MHz 200 MHz B4 200 MHz 1 GHz B5 1 GHz 3 GHz B6 In that testing the procedure was: a. Set the PMT grounding configuration by making the appropriated jumping points connections. b. Set the spectrum analyzer frequency band. c. Acquire background noise inducted on the PMT circuitry. d. Save data on disk. e. Repeat the measuring process for the other 5 frequency bands. The CIEMAT RF background has been determined, as a matter of calibration, using a unidirectional wide band antenna as well. This measurement gives a stand point, serving as reference, being used as a comparison base. The second test was designed to determine the PMT circuit transfer function, figure 4 presents the experimental setup. 220 k Ohm 22 m RG303/U cable 20 m RG58 cable DChooz Splitter OUT +HV PMT ROHDE & SCHWARTZ ZVB4 Vectorial Network Analyzer Figure 4. Experimental setup for the second test.

12 In the present study, the transfer function is a representation, in terms of temporal frequency, of the relation between the input or excitation signal and output signal of the PMT circuitry, assuming it as a time invariant system. Port 1 of the ZVB4 Network Analyzer replaces the PMT and the PMT base, working as a signal source (Zout = 50 Ohm). Port 2 receives the electric signal coming from the PMT splitter output. The measurements were done in different bands, assuring resolution and sensibility, table 3 presents those frequency bands. Different PMT splitter grounding configuration has been tried as well. During the second test was employed the same experimental procedure, for grounding configuration changing, as in the first testing. Table 3. Second test frequency bands (sweeping bands). Band # Start frequency Stop Frequency S1 300 KHz 2 MHz S2 1 MHz 50 MHz S3 50 MHz 200 MHz S4 200 MHz 1 GHz Results Discussing the First Test Before starting the PMT circuitry measurements one have proceed a sort of calibration routine. The spectrum analyzer input has been connected to a 50 Ohm standard load. The background noise test was performed in six bands (see table 2), the results are showed in figure 5. A

13 B C

14 D E

15 F Figure 5. Noise spectra for a 50 Ohm standard RF load at CIEMAT EMI laboratory. (A) scanning on Band1 from 9 K to 100 KHz, (B) scanning on Band2 from 100 K to 2 MHz, (C) scanning on Band3 from 1 M to 10 MHz, (D)scanning on Band4 from 10 M to 200 MHz, (E) scanning on Band5 from 200 MHz to 1 GHz, (F) scanning on Band6 from 1 G to 3 GHz.

16 No intrinsic constant noise or intermittent noise structure is detected, the ADVANTEST R3132 Spectrum Analyzer, was used in first test, works fine on long term measurements and have a perfectly repetitive behave. As a second step in the measuring system calibration, the spectrum analyzer was connected to a omnidirectional wide band antenna. The CIEMAT RF background was determined for the same six bands (see table 2), the results are showed in figure 6. A B

17 C D

18 E F Figure 6. A) scanning on Band1 from 9 K to 100 Khz, equipments and controlling systems, (B) Band2 from 100 K to 2 MHz AM radio broadcasting (C) Band3 from 1 M to 10 MHz; industrial noise (D) Band4 from 10 M to 200 MHz; FM radio, citizen band, police, fire department and civil services broad casting, (E) Band5 from 200 MHz to 1 GHz; TV broadcasting, radio beacon, civil safety service and GSM 900 downlink, F) Band6 from 1GHz to 3 GHz, high frequency applications and microwaves.

19 The antenna RF measurement gives a good understanding about the kind of electromagnetic noise background one will face on CIEMAT facility. The six bands scanned cover a broad portion of human activity noise sources in cities ground. Following the test procedure, the PMT circuit has been connected to the spectrum analyzer and the grounding configuration was set (Jumping point A closed, Jumping point B open, box GND connected to the PCB, metal box open), the test has been done for the six bands. Table 4 presents all measured configurations. Table 4. First EMI testing configuration. (for scanning bands see table 2) Grounding Config. # Jumping point A Jumping point B Metal Box GND Metal Box covering Scanning Frequency Bands 1 Closed Open Connected Open B1 B6 2 Closed Open Connected Closed B1 B R Open Connected Closed B1 B5 4 Closed Closed Connected Open B1 B5 5 Closed Closed Connected Closed B1 B5 All results are very similar, no grounding configuration presents a special pickup noise response. In the other hand, open or closed by the aluminum plate the PMT splitter has the same level of induced background noise. Both facts seems indicate that most of the pickup noise measured is due to the antenna behave of the quite long (60 m) cabling, in figure 7 one can see the results for the test configuration number 4. A

20 B C

21 D E Figure 7. PMT circuitry noise spectra for grounding configuration number 4 at CIEMAT EMI laboratory. (A) scanning on Band1 from 9 K to 100 Khz; its possible see a bump at 97 Khz due to industrial noise, (B) scanning on Band2 from 100 K to 2 MHz; the red circle marks the AM radio band centered at 920 KHz, (C) scanning on Band3 from 1 M to 10 MHz, (D)scanning on Band4 from 10 M to 200 MHz; the red circle marks the FM radio band, (E) scanning on Band5 from 200 MHz to 1 GHz; the red circle marks (500 MHz) noise probably due to radio beacon, blue circle marks (930 MHz) GSM 900 downlink from base station to mobile station.

22 This particular configuration was choosen as example, because connecting jumping points A and B at once, one is creating a ground loop on top of the PCB. The ground loops are notable by it capacity of enhance pickup noise, being a mutual inductance structures. The scanning of frequency Band1, from 9 K to 100 KHz (figure 7A) shows a bump at 97KHz (red circle) possibly due to industrial noise sources, this band was expected to be a quite band, nevertheless measuring equipments, general propose instrumentation, switched powers supplies or digital processing apparatus could irradiate at those frequencies. In Band number 2, from 100 KHz to 2 MHz, the red circle (figure 7 B) marks the AM radio, these band is centered at 920 Khz. The AM radio radiative field could penetrates building and tunnels as well. The antenna measurement shows an AM signal of 73.3 db at CIEMAT, the PMT AM pickup noise is 75.4 db, confirming the concerning that this kind of RF noise penetrates building structures and the PMT system shows very low AM radio noise immunity ( 2.1dB). Scanning on Band3, from 1 M to 10 MHz, also call the industrial noising band, its expected to have the contribution of powers supplies, motor starting and speed control system, heavy mechanical devices power system, Foucaut current based devices etc, but no activity has been noticed. In frequency band number 4 (10 M to 200 MHz) the red circle marks the FM radio band (see figure 7 D). The antenna FM signal level is 53.9 db at CIEMAT, the PMT FM pickup noise has 68.3 db level, the PMT system shows a better noise immunity ( 14.4 db) compared to AM radio noise. The last band scanned for grounding configuration 4, is the frequency band between 200 MHz and 1 GHz, the red circle (figure 7E) marks (510 MHz), this noise structure is probably due to a radio reference signal as a radio beacon. A radio beacon is a transmitter at a known location, which transmits a continuous or periodic radio signal with limited information content, on a specified frequency. The blue circle marks the 930 MHz centered band, characteristic of the GMS 900 downlink communication from the base station to mobile station. Its important mention the fact in Band6, from 1 G to 3 GHz, no noise structure has been detected in test configuration number 1 and 2, for these reason that measuring band has been disregarded. Discussing the Second Test Using the Vectorial Network Analyzer the transfer function is automatic determined by this instrument, in addition it is possible to measure the signal reflection characteristic of a given quadrupole as function of the frequency. The second test consists of a series of transfer function and reflexion measurement, where the PMT and the PMT base were replaced by the analyzer port # 1 and port # 2, used as signal output and measuring input respectively, on both cases the nominal impedance was 50 Ohm. Table 5 summarizes the different measuring done during this testing, the sweeping frequency bands (Sn) are the same presented on table 3.

23 Table 5. Second EMI testing configuration. (for sweeping bands see table 3) Grounding Config. # Jumping point A Jumping point B Metal Box GND Metal Box covering Sweeping Frequency Bands 1 Closed Closed Connected Closed S1 S4 2 Closed Open Connected Closed S1 S R Open Connected Closed S1 S4 4 Open Closed Connected Closed S1 S4 Figure 8 shows the transfer function for four frequency bands (S1 to S4 (see table 3) the behave is absolutely well understood. In the first band ( 300KHz to 2MHz) the PMT circuitry acts like a high pass filter up to 1MHz, just like a capacitor in series with a resistive load, afterwards a inductive characteristic start dominating the circuit behave. From this frequency band on, meaning the consecutive bands (S2 to S4), the inductive behave is dominant, mostly due to the long coaxial cabling. The important result of these measurement is the fact that there is no resonance structure in the whole frequency interval spectered and no overshot or ringing oscillation as well. A

24 B C

25 D Figure 8. PMT circuit transfer function in four different frequency bands. (A) sweeping frequency S1 (300 KHz to 2 MHz), (B) sweeping frequency S2 (1 MHz to 50 MHz), (C) sweeping frequency S3 (50 MHz to 200 MHz) and (D) sweeping frequency S1 (200 MHz to 1 GHz). In figure 9 is showed an example of signal reflexion spectrum (from 1 to 50MHz), in that figure one can see the signal reflexion modes for the PMT output signal connected to the PMT splitter. That particular frequency range has been selected for being part of the essential PMT light signal bandwidth. Figure 9. Signal reflexion spectrum from 1 to 50MHz for the PMT output signal connected to the PMT splitter.

26 Conclusion In this report is presented an electromagnetic compatibility and noise testing for the DoubleChooz PMT system. It was possible to proceed the EMC testing on different grounding configurations of the PMT splitter due to its special PCB design, endowed of jumping points and a metal box ground electrode. Two different tests of the DChooz PMT system are presented. In the first case the local background electromagnetic noise was used as excitation source, in the second case, the test was designed to determine the PMT circuitry transfer function. In the first test calibration routine (induced noise in a 50 Ohm standard load) no intrinsic constant noise or intermittent noise structure was detected. Following the calibration routine an omnidirectional antenna was used to determine the local (CIEMAT Madrid) RF background, these data could also be used as a reference with comparison meaning. In the first test all results are very similar, no grounding configuration presents a special or better pickup noise immunity. Open or closed by the aluminum plate the PMT splitter has the same level of induced background noise, what seems indicate that pick up coupling is caused by the cabling. Scanning in frequency Band1 shows no special noise structure. On Band2 AM radio band can be seen, compared with the antenna noise measurement its possible see an attenuation of 2.1 db, indicating a low immunity to noise in that particular RF band. Observing Band3 characterized by industrial noising, no activity is measured. On band number 4 the FM radio band is present and the observed attenuation compared to the antenna measurement is of 14.4 db, better then in the AM band case. On the last band scanned Band5 one can see noise at 500 MHz, probably due to radio beacon and at 930 MHz tipical of (GSM 900) downlink. On Band6 no noise structure has been detected. In the second test the transfer function was done in four different bands, in the first bans ( 300KHz to 2MHz) the PMT circuitry acts like a high pass filter up to 1MHz, afterwards a inductive characteristic start dominating. No resonance structure was observed in the whole frequency interval spectered and no overshot or ringing oscillation as well.

27