Transcript

EMC review for Belle II

(Grounding & shielding plans)

PXD –DEPFET system

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

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

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

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 ?

2. Grounding strategy - Topology

PXD

Detector

• 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.

2.1 Grounding strategy - Implementation

Detector (FEE)

Cooling block

Beam pipe ?

Reference ground

Cooling pipe

Hybrid Equivalent to Multi-point

Junction Box

or

Patch panel

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).

Use of vias interconnecting grounds

may help lower RF impedance

• 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.

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

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.

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

PXD

System

SVD System

• 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

3. Noise emissions

DEPFET VOLT

DCD VOLT

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

Load

Power switching converter

Switching devicesFilter

Idm

Gnd

Load

Power switching converter

Switching devicesFilter

Idm

GndGnd Gnd

Power switching converter

Parasitic capacitance of heat sink

Switching devices Filter

Icm

CM Filter

Gnd

Power switching converter

Parasitic capacitance of heat sink

Switching devices Filter

Icm

CM Filter

DM CM

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.

3. Noise emissions: Test plans

• Output currents –

(ref. = 50 ohms)

Cm

Cd Id

Icm/2 Icm/2

I+

Icmmeas

+

-

• 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

4. Noise immunity issues

Optical Link

Voltage Distribution Detector DHH P.S.

Noise source

Victim

Coupling path

FEE PP

Optical link

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).

Zdet

Zfeedback

Ig

Vsource

VAmplow

V-

Vout

signal • The most important elements of the signal

circuits are:

– Trans-impedance amplifier

• Low Gain (1,2,3 or 4)

– It is an advantage for PXD !!!

– Impedances associate to this circuit

• Real & stray

4. Noise immunity issues: Signal circuit

),( sdsource LCfZiIs

),( sdamplow LCfZ

iAmplowI

sourceV

AmplowV

cableZ

logAnaGND

.: AmpSoGndZ

),,( fBAfV loopinduced

4. Noise immunity issues: Signal circuit

Equivalent signal detection circuit

),( ggGates LCfZ

,...., cleargate VV

• 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 .

4. Noise immunity issues: Test plans

Counts

/mA

Frequency

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

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

5. Cabling

• Three type

of cables.

– Cable 1

– Intermedi

ate cable

– Kapton

cable

5. Cabling

• Three type of cables will be used in DEPFET system

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

6. Conclusions