1. Transient Waveform Recording Utilizing TARGET7 ASIC
J. Zhang, S. Liu*, Y. Wang, C. Yang, X. Zhu, C. Feng
University of Science and Technology of China
Presented by Yu-Wang(Nick)
Good afternoon everyone. With today’s technology, more and more electronics element such as cellophane and computer become smaller and smaller, and what we have done is to make detectors smaller
15’(0:00-0:15)

2. Signal In Real World and Computer
Analog signal in real world
Such as sounds
Hard to store and process
Digital signal in computer
Computer only know 0 and 1
Easy to store
Computer can process
Convert analog signal to digital signal
Need an element: ADC(Analog-Digital Convertor)
In electronics world, the most important thing is to convert analog signal to digital one. All the signal in real world we call it analog signal, such as sound and movement, it’s hard to store and can only be processed by human. The signal that computer can understand we call it digital signal, it is just 0 and 1. It’s easy to store and can be processed by computer quickly. The element between analog and digital we call it Analog-Digital Convertor (short as ADC)
40’(0:15-0:55)
2018/1/30

3. Technology In Particle Detector
Traditional way
Cannot get the waveform
Record the amplitude of the signal
Advanced way
Record the waveform using fast ADC
Only record one waveform in one chip
Our new way
Record 16 waveform in one chip
In traditional way, particle detector can not record the waveform of signals, it can only record the amplitude of the signal, so that lots of information is lost. In recent years, an advanced way has been developed. With the help of fast ADC, detector can record the waveform of the signal. Waveform means more accurate measurement and more information. But modern physics experiments need to record tens of thousands signal at one time. We have developed a new method to achieve this goal.
40’(0:55-1:35)
2018/1/30

4. TARGET-7 ASIC ASIC(Application-Specific Integrated Circuit) TARGET-7
An integrated circuit (IC) customized for a particular use
TARGET-7
An IC designed for high-speed and multi-channel particle detector
16 input channels
Can convert 100 billion signal in one second
Just as big as a coin
We used an ASIC to realize this. An ASIC is an integrated circuit customized for a particular use. Our TARGET-7 ASIC is an IC for high-speed and multi-channel particle detector. It has 16 input channels and just as big as a coin. Target7 can convert 100 billion times in one second.
30’(1:35-2:05)
2018/1/30

5. Detail of TARGET-7
It has two main parts, the analog and digital part. The analog part has 16 input pins. Due to the switched-capacitor array(short as SCA) the analog part can store 2^16 signals, we call this kind of store acquisition. The digital part use 16 Wilkinson ADC to convert the analog signal. It uses a method called ping-pang way to reach 100 billion sample rate.
40’(2:05-2:45)
2018/1/30

6. Design of the Test-Board
Use FPGA to Control as Master
FPGA:
CPU like element,
Can process multiple task at one time
Structure of Test-Board
Signal
Control
Command
Data
The first step of our work is to design a test-board for target-7. We use an FPGA to control the Target-7.This is the structure of out test-board. The computer send a command to the FPGA, then the FPGA control the Target-7 to convert the signal. When the conversion is done, the FPGA get the data and transfer to the Computer
30’(2:45-3:15)
Data
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7. DC(Direct Current) Transfer Function
Relation Between Signal and Data
ADC counts is a function of input signal
Result
Linear voltage:0.5~1.8V
552 to 3785 ADC counts
11.6-bits resolution
The next step is testing the board. This is the DC transfer function of out board. DC means direct current. The ideal function line should be linear. We measured our test board and get the linear voltage area which is 0.5V~1.8V. This represents 11.6-bits resolution. It corresponds this area in the figure. Also we can see, there are many nonlinear factors.
40’(3:15-3:55)
2018/1/30

8. Voltage Calibration
We need to do some calibration to correct the nonlinearity. The 16 channels have different offset and this will cause mismatch. A more important reason to calibrate is there are differences among the storage cells. These differences may cause serious distortion. So that, we developed series of methods to calibrate the voltage. We calibrate every cell individually and use polynomial fit to get the calibration parameters.
40’(3:55-4:35)
2018/1/30

9. Voltage Calibration Result Before calibration After calibration
These figures show the result of the calibration. Two of the upper figures is the signal without calibration. There are serious nonlinearity and distortion in the signal. The lower two figures is the signal after calibration. There is no distortion on it and the nonlinearity is 1%. The calibration is effective.
30’(4:35-5:05)
2018/1/30

10. AC(Alternating current) Performance
AC Transfer Function
Using sinusoidal signals as input
Linear in low amplitude(<0.6V)
AC saturation happens in high amplitude(>0.6V)
Another important parameter we care about is the AC performance, AC means alternating current. We use sinusoidal signal as input to test the AC transfer function. It show that when the signal is smaller than 0.6V, the function is linear. Nonlinearity happens when the signal is over 0.6V
40’(5:05-5:45)
2018/1/30

11. Application in Charge Measurement
Most important information
Recording charge waveform
Measurement method
Use CSA(Charge Sensitive Amplifier) and shaper to collect charge
Compared with Oscilloscope
Then we applied our test-board to charge measurement. What we need to do is to record the charge waveform to get full information. We use a signal generator to generate the charge signal. Then we used a charge amplifier to change it into waveform. To get more accurate result, we compare our result with an advanced oscilloscope.
35’(5:45-6:20)
2018/1/30

12. Application in Charge Measurement
Result
Nonlinearity of TARGET7 is 0.6%
Better than oscilloscope 0.1%
These two figures is the result of our test. The red waveform on the left figure is recorded by Target-7, and the black one is the result of oscilloscope. It’s clear to see that our result is 2 times more accurate than the oscilloscope. The right figure is the comparison of the nonlinearity. The nonlinearity of our test-board is 0.6%, better than the oscilloscope. The accuracy satisfies the requirements of particle experiments.
40’(6:20-7:00)
2018/1/30

13. Conclusion1
We have designed a 16-channel 1GSPS waveform digitizer with TARGET7 ASIC
The dynamic range is 1.8V
DC noise is 1.76mV
After DC calibration, nonlinearity is 1.1%
Timing resolution is 152ps
In conclusion, the goal of our research was to design a multi-channel high seed waveform digitization system.
As shown before, utilizing Target-7, we completed this goal. After this we have tested the performance of Tartget-7 and we designed a method to calibrate Target-7
These are parameters we measured. All these parameter is better than the requirements of particle experiments.
35’(7:00-7:35)
2018/1/30

14. Conclision2 We have applied the TARGET-7 to charge measurement
The waveform record is better than the same speed Oscilloscope
The nonlinearity of charge measurement is 0.6%
We succeed to apply the Target-7 to charge measure experiments. The result show that our system is better than the same speed oscilloscope, the nonlinearity of our system is 0.6%.
20’(7:35-7:55)
2018/1/30

15. Future Work
Some experiments needs millions of channels, and Target-7 ASIC is an optimal option.
We need to test other ASIC as well as Target-7
New calibration methods are under investigation
The final goal of our research is to apply waveform digitization method to the large-scale particle detection such as cosmic-ray detection and collider experiment. In these experiments, physicists need millions of channels to get experiment data. At present the Target-7 ASIC is an optimal option to realize the goal.
In the feature research, we have two directions. One is to utilize more Tartget-7 ASIC in one system to achieve more channel acquisition. The other is to do research on higher integration density ASIC to get more data in one ASIC.
At the same time, we are investigating new calibration method to get more accurate calibration.
Thank you! Are there any question?
55’(7:55-8:50)
2018/1/30