EMC review for Belle II (Grounding & shielding plans) PXD DEPFET system

Transcription

1 EMC review for Belle II (Grounding & shielding plans) PXD DEPFET system

2 Outline 1. Introduction 2. Grounding strategy Implementation aspects 3. Noise emission issues Test plans 4. Noise immunity issues Signal circuit Test plans 5. Cabling 6.Conclusions

3 1. Introduction PXD- DEPFET detector is very complex FEE (Sensor, DCD,DHP) It may be sensitive to EM noise It may radiates ( HF clocks and signals) Power supplies It emits EM noise Cable & connectors It may propagate EM noise inside/outside FEE area

4 2. Grounding strategy It is focused on grounding and shielding aspects. It plans to define: Safety grounding Signal or ground reference plane Grounding topologies These issues will be used to verify: Electrical safety issues Identify possible ground loops Identify EMI sources Identify EMI victims

5 2. Grounding strategy Selection of reference Any metal structure Local GND (Cooling blocks) It should have low impedance from DC to High frequency Safety ground & Equipment protection Ground path should be free of operational currents Laboratory codes and standards at KEK - Any? Metal parts that can be energized should be grounded Ground connections - Bonding and straps An EMC program has been implemented for the machine EMC PROGRAM ON THE ACCELERATOR RINGS K. Okamura (KEK), Y. Watanabe (JAEA) It is mainly focused on grounding issues only Should we apply the same rules?

6 2. Grounding strategy - Topology PXD Detector

7 2.1 Grounding strategy - Implementation PXD connected to the cooling blocks via capacitors High Frequency Ground Connection Cooling blocks connected to Beam pipe? through direct bonding. Beam pipe connected to reference ground system. Junction Box or Patch panel Detector (FEE) Cooling block Cooling pipe Beam pipe? Hybrid Equivalent to Multi-point Reference ground

8 2.2 Grounding topology: Grounding implementation - Capacitors Capacitors are required to: - Provide an AC connection to ground. - Decouple the power feeds. They have to be prepared to operate at High-frequency, low-inductance ceramic capacitors (0.1 µf over 10 MHz). The decoupling capacitor should be located as close as physically possible from the IC s power pin. Bulk capacitors: at least ten (10) times greater than the sum of all the values of decoupling capacitors. Use of vias interconnecting grounds may help lower RF impedance

9 2.2 Grounding topology: Grounding implementation - Straps Multiple equipment or units must be connected to a signal reference system (SRS) for direct connection bonding straps are required Bounding straps: impedance highly influenced by inductance L, dependent on geometry resonances must be avoided Local ground at detector level (HF conection) Short connections

10 3. Noise emissions Main external noise sources for PXD will be conducted noise Conducted : Power supplies - Switching power converters CM currents from neighboring systems (SVD) Radiated noise (inside SVD + PXD volume) No big far field emissions are expected because distance and frequency. F=100 MHz - λ =3 m / - Rule λ /3= 1 m Near field Magnetic field noise emissions may be the predominant ones because noise currents and low voltages inside PXD volume.

11 3. Noise emissions Most of the external noise sources will be couple to the PXD via cables Most probable path - Power cables (LV) Low impedance path Other cables may introduce noise but filtering is easier because they high impedance cables Data and slow control lines. Conductive ground structures may conduct some noise CM emissions from other subsystems SVD System PXD System

12 3. Noise emissions PS system of PXD is very complex Power is supplied remotely by several floating DC-DC converters Stefan Rummel s talk This PS emits noise DCD VOLT DEPFET VOLT

13 3. Noise emissions Switching converters generates conducted noise At the input & output It is generally the main noise source in HEP Two modes of noise emissions (khz - MHz range) Common mode & Differential mode Power switching converter Power switching converter Switching devices Filter Switching devices Filter CM Filter Idm Load Icm Parasitic capacitance of heat sink DM Gnd CM Gnd

14 3. Noise emissions: Test plans Detailed test plan is planned to measure the noise emission level of the power supply units It will help to define the compatible levels with the FEE. A prototype of the power units is required Special test setup It will require special connectors and cables Test load - A set of resistors Electronic loads are noisy. Noise at the output and input of Power units will be measured with EMI probes and spectrum analyzers This test is planned to be carried out in September 2012 or October 2012.

15 3. Noise emissions: Test plans I+ Id Cd Cm + - Icmmeas Icm/2 Icm/2 Output currents (ref. = 50 ohms)

16 4. Noise immunity issues The immunity of the system is defined main by the sensitivity of the FEE The Front-End electronics is the most susceptible part to: Radio frequency perturbation (conducted and radiated) Transient perturbation. The signal circuit defines the robustness of the FEE to any noise in the system. Other system may be affected by noise but based on previous experience, signal circuit is the most sensitive one. Any noise in this circuit may increase noise baseline at the output of each channel Victim P.S. Voltage Distribution DHH PP FEE Detector Noise source Coupling path Optical link Optical Link

17 4. Noise immunity issues This noise defines the minimum signal level that the FEE can process Thermal noise dominant effect (by design) EM noise has to be characterized and minimized EM noise contribution depends on two factors It depends on Front End Amplifier frequency response. Coupling mechanisms (coupling network) between EM noise and output of the FEE. EM noise contribution is not constant. It may change from hundreds khz to several MHz FEE characterization to EM noise help to improve the FEE immunity (identify weak areas & frequencies).

18 4. Noise immunity issues: Signal circuit signal Zfeedback The most important elements of the signal circuits are: V- Vout Trans-impedance amplifier Low Gain (1,2,3 or 4) Ig Zdet VAmplow It is an advantage for PXD!!! Impedances associate to this circuit Vsource Real & stray

19 Z 4. Noise immunity issues: Signal circuit source f ( Cd, Ls ) V induced f ( A, B, f ) loop Is i V source Z cable Z Gnd : So Amp. V Amplow Z amplow f ( Cd, Ls ) GND Analog I Amplowi ZGates f ( Cg, Lg ) V gate V,..., clear Equivalent signal detection circuit

20 Counts/mA 4. Noise immunity issues: Test plans The characterization of EMI contributions due to external noise is performed via immunity test on prototypes Weak points & Noise characterization Compatibility The idea is to inject noise into the system via external lines. Different frequencies and amplitudes This measurement will define the transfer function between noise and FEE output. Frequency

21 4. Noise immunity issues: Test plans Two sets of test are planned: First set of immunity test an a preliminary prototype system of DEPFET. It is planned for end September 2012 at Bonn University. Second set of test are planned on a full prototype of DEPFET system It will be performed in similar way than a test beam Full system operation. It is planned for mid 2013 at ITA facilities

22 5. Cabling Belle II and any HEP experiment have a large amount of cables installed in a small volume. These cables are very different Voltages - LV (V ) to Bias Currents - Low currents (ma) to High Currents (several amps) Signal & power Attention should be paid in the cabling coordination because it may lead to some integration problems. Interference phenomena High frequency Transient effect Low frequency phenomena Destructive effects

23 5. Cabling Three type of cables. Cable 1 Intermedi ate cable Kapton cable

24 5. Cabling Three type of cables will be used in DEPFET system

25 5. Cabling. Somes studies are planned to define the key parameters and the configuration of the power distribution network to minimize the conducted noise. These studies and analysis will be based on: Numerical models developed in MATLAB codes. It will help to address the effect of power cables on the noise propagation and the impact that those cables have in the selection of: EMI filters for the FEE low-voltage input Conducted emission levels required for the power supplies. Shielding connection

26 6. Conclusions