1LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +Anatoli, Michail
( Michail Soldatov is electronics expert, one of the CALO HV systems designer IHEP, Protvino)
Introduction
• As was discovered, the ECAL CW base design has some features lead to a HV output non-stability and noise impact to a PMT anode.
• An additional PSPICE simulation of the ECAL CW base has been done and a modification proposal for detailed study is suggested.
• The scope test of the ECAL CW shows a charge pick-up on the OA inputs, an integration chain (same as in HCAL CW base design) has been added. The proposed for ECAL circuit now is the HCAL circuit with optimized RC integration chain.
• Five modified ECAL CW bases were studied with scope and showed the same behavior.
• Additional solutions have been simulated and results are shown in backup slides:
1. CW base version working with OA operated in switching mode, but in linear regulation mode.
2. An optimized ECAL version with OA operated between linear and switching mode.
2LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +Technical details.
The CW base circuit that we study has two operational modes:
1. OA in linear mode and it controls the discharge current throw the transistor Q1. Q1 operates in switching mode with a pumping frequency (60 kHz). Few years ago the HERA-B CW base design has been optimized for HCAL application working in linear mode. Two capacitors with not clear functional meaning have been removed and internal to OA integration chain added for the OA regime stabilization.2. OA works in switching mode (some designers are using a digital comparator integrated circuit instead of OA). Q1 operates in switching mode too but with different frequency defined by a feedback delay. There is a sub-mode for this operational mode.When a charge is applied to the OA input through some capacitance, the circuit works in switching mode with 60 kHz frequency, but in addition a low frequency is presented. This is an original ECAL CW base design.
Analysis ECAL CW base behavior, PSPICE simulation and scope study of the five CW bases with tubes show that for current ECAL CW base implementation the linear mode is preferable.
3LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Disadvantages of the switching mode operation for the current ECAL CW base design are following:
• HV output dependence versus LV power supplies;
• HV output voltage shift, due to a charge injection to the OA input;
• For CW base operating in linear mode the multiplication coefficient Coe must be:
HVout = Coe*Uctrl + Ushift,
Coe = (Rfb / (Rin * 4)) * 22 (= 425.8),
where Rfb is feedback resistor of 4800 k, Rin is 62 k.
HCAL
• An addition the low frequency oscillations of the HV output could be appeared for some values of the control and middle voltages (see slides 18,19)
My report “Status HV System based on CW base for HCAL Application”, on LHCb meeting 21.05.03
U Photocathode vs U control for five CW HCAL bases
y = 427.6x + 8.95
500
700
900
1100
1300
1500
1700
1900
2100
0 1 2 3 4 5 6
U control V
U p
h V
k21
k22
k23
k24
k25
Linear (k21)
4LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +PSPICE Simulation conditions:
• The main point of the simulation is study the behavior of the HV Output from different factors.
• Few factors affected on HV output were applied in simulation:
1. Control voltage change from 1 V to 1.5V (in time 55 ms);
2. Output load current change from 0 to 10 mkA (in time 80 – 90 ms);
3. LV power change from (+-) 5 V to (+-) 6.5 V (in time 100 – 130 ms);
4. Parasitic capacitance from switching transistors to OA input is simulated by capacitor C20 = 0.1 pF.
Next slides illustrate the simulation results:
Slide_6 is an overview of the all simulation time.
Slide_7 is zoom of the time interval when a control voltage changes.
Slide_8 is zoom of the time interval when an output load current changes.
Slide_9 is zoom of the time interval when LV power changes.
Slide_10 is zoom of the time interval with detailed view of the signal shapes of some internal points.
5LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
10
-5V -> -6.5V5V -> 6.5V
1V -> 1.5V
100 V
HV Output
Simulated CW base circuit diagram
Parasitic capacitance simulated a PCB cross talk
6LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Overview of the simulation time
7LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Control voltage change from 1 V to 1.5V (in time 55 ms);
8LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Output load current change from 0 to 10 mkA (in time 80 – 90 ms);
9LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
LV power change from (+-) 5 V to (+-) 6.5 V (in time 100 – 130 ms);
10LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Zoomed time interval with detailed view of the signal shapes of some internal points.
11LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
OA output signal and Q1 collector comparison
Scope measurement and simulation result
Conditions: HV_out = 480 V, I_load ~ 0 mkA.
12LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Scope measurement and simulation result
OA output signal and HV ripple after CW fifth stage comparison
Conditions: HV_out = 480 V, I_load ~ 0 mkA.
Ripple < 80 mV
Ripple < 100 mV
13LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Scope measurement of the chained tubes
Pumping frequency correlation for chained tubes. Green trace OA output of CW 1.
1
2
3
Correlation between CW_1 – CW_2
Correlation between CW_1 – CW_3
Not Correlated
Correlated
14LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
CW base output ripple for three sequentially connected tubes is about 1.5 V pick to pick, but with high load current.
Scope measurement
Conditions: HV_out = 480 V, I_load ~ 48 mkA.
15LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
ECAL CW base modification:Six points of soldering
• Add R16 = 5.6 k in serial with C5
• Remove wire and add R2 and C1 (see circuit diagram)
Add wire to connect two ground lines
Remove C17Remove C2
16LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Conclusion
The ECAL CW base modification, proposed by me and Michail, is the HCAL design with optimized integration chain.
The circuit simulation is very good matched with the scope measurements.
Simulation shows that C1*R2 time constant could be in wide range from 5 to 30 mks.
Six soldering operation will be needed for one base modification, but in my opinion, much more time will be needed for dismounting and mounting PMTs.
There is good indication that modification of the ECAL design to HCAL one allows to have the same CW performance. Fifteen hundreds (quota of ECAL amount) of the HCAL CW bases are working now.
17LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Low frequency oscillation of the near original ECAL base.
Simulation of a CW base version working with OA operated in switching mode.
Simulation of an optimized ECAL version with OA operated between linear and switching mode.
18LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Low frequency oscillation of the near original ECAL base
OA is operating in switching mode with low frequency. C1=2 pF; R2=50k; C21=0 pF; c17=1nF
CW base Simulation.
19LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
OA is operating in switching mode with low frequency. C1=2 pF; R2=50k; C21=0 pF; c17=10nF
Simulation and scope test comparison.
Low frequency oscillation of the near original ECAL base
20LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of a CW base version working with OA operated in switching mode.
OA is operating in switching mode.
C1=2 pF; R2=50k; C21=2 pF; c17=0
21LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of a CW base version working with OA operated in switching mode.
22LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of a CW base version working with OA operated in switching mode.
23LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of a CW base version working with OA operated in switching mode.
F = 30 kHz
24LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
F = 60 kHz
Simulation of a CW base version working with OA operated in switching mode.
25LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
26LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of an optimized ECAL version with OA operated between linear and switching mode
Two cases were simulated:
C21 = 300 pF; C17 = 47 nF; C1 = 0; R2 = 0;
C21 = 300 pF; C17 = 47 nF; C1 = 100 pF; R2 = 50 k;
27LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
C1 = 100 pF
Simulation of an optimized ECAL version with OA operated between linear and switching mode
28LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of an optimized ECAL version with OA operated between linear and switching mode
29LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
C1 = 0.0001pF
Simulation of an optimized ECAL version with OA operated between linear and switching mode
30LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Simulation of an optimized ECAL version with OA operated between linear and switching mode
Conclusion
31LHCb CALO commissioning meeting 18.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
32LHCb CALO commissioning meeting 28.08.08 Anatoli Konoplyannikov /ITEP/
Proposal of the ECAL CW base modification +
Study to be continued.