* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Documentation for GAIN setup
Index of electronics articles wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Power MOSFET wikipedia , lookup
Schmitt trigger wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Regenerative circuit wikipedia , lookup
Power electronics wikipedia , lookup
Trionic T5.5 wikipedia , lookup
Two-port network wikipedia , lookup
Surge protector wikipedia , lookup
Current source wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Automatic test equipment wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Wilson current mirror wikipedia , lookup
Tektronix analog oscilloscopes wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Charlieplexing wikipedia , lookup
Operational amplifier wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Current mirror wikipedia , lookup
Documentation for GAIN setup Basic theory Gain calculation of avalanche photodiodes (hereafter referred as ‘apds’) is done by measuring the output current of the apd while applying different bias to it and dividing the difference from light current to dark current by the difference at gain one (usually at <30V). (Note: For the operation of the setup please refer to the lab manual for the setup) Description of the Gain setup The heart of the gain setup is the aluminum box which houses the light distribution fibers mounted on the aluminum base plate which is through holed for water chilling and fits the circuit housing 20 apds on its base so that the apds are very close to the aluminum for air contact chilling. This whole apparatus is covered with a thermal shield of aluminum, foam and aluminum in that order to ensure thermal stability irrespective of room temperatures. Chilling for the setup is provided by Neslab RTE-111D chiller through the two tubes for the water flow. A AD590 temperature sensor mounted very close to the apds monitors the setup temperature. APDs are mounted on the 20 channel circuit in the ZIF sockets and can be screwed to the base of the aluminum plate. Voltage is applied to each individual apd one by one while the others are not under bias so as to reduce leakage currents. Keithley 7001 switch system with two Keithley 7154 HV switching cards are used to switch the apds. The currents are precisely read by the Keithley 487 and it also provides the bias for the apds. The light output is monitored in conjunction by a PIN diode using a Keithley 485. The labview program takes data and calculates the gain, dM/dV and stores it in an ASCII text file on the local machine and also in the cristal database. Calculation of Gain, dM/dV and dM/dT For Gain 1 calculation four readings starting from the index 3 of the voltage array. For example if the first stop at V is 60 with a 5 V step width the mean will be of values at 25, 30, 35 and 40V, since in this case of the settings in the front panel diagram the start at V value is 10V, therefore index 0 is 10V index 1 is 15V and so on till index 3 to 6 are 25 to 40V. The gain equation used is (Itotal-Idark)/Mean of the 4 values(Itotal-Idark). The gain at 50 is found by interpolation among the closest set of values for gain. dM/dV is measured by dM/dV * 1/M = (Mn - Mn-1)/(Vn - Vn-1)/(Mn+Mn-1) * 200 where M is the Gain and V the bias. dM/dT is not calculated by the program and needs to be separately done since the program was initially designed for only single temperature. The equation to be used is 1/M(dM/dT) = -100/(Avg M for the two temperatures)*((M at temp 1- M at temp 2)/2) Detailed description of the settings and instrumentation Data Acquisition with National Instruments AT-MIO-16XE and BNC-2090 National Instruments AT-MIO-16XE card is used in with a BNC-2090 adapter to bias three 470nm Nichia LEDs that supply the light. The typical light currents read by hamamatsu apds at ~25C with respect to the bias are as follows: LED Bias APD Current (G=1) APD Current (G=50) PIN Current 2.72V 25-35nA 500-800nA 50-75nA 2.92V 30-40nA 1-2A 75-85nA Also the temperature sensor is monitored by the BNC-2090. The PIN photodiode is biased by the BNC-2090. Settings currently used on the BNC-2090 with the Gain setup are as follows. ACH0 Temperature Sensor Analog Input (10V range, Single ended, SE setting on the BNC-2090 adapter) DAC0OUT LED Bias Analog Output (-2.92V or , RSE setting) DAC1OUT PIN Bias Analog Output (~5V or , RSE setting) Test panel for the BNC-2090 can be found from StartProgramsNational Instruments DAQNI-DAQ Test Panels or from the Devices and instruments option in the measurement and automation explorer. There are no configurable hardware settings on the AT-MIO-16XE DAQ card. Software settings are generally automatic with Windows NT but in case of problems one can reassign them from the control paneldevices by trying to uninstall and reinstall. GPIB (IEEE 488.2) card National Instruments AT-GPIB/TNT Current settings for the switch are as in the table below, these correspond to the software hex address of 0x2c0 for the card. Also the DMA is set to 5 for which the DRQ5 and DACK5 are jumpered. And Interrupt level 10 is selected by jumpering IRQ10. A9 OFF A8 ON A7 OFF A6 OFF A5 ON Note: The picture below is just to show the position of the switches on the GPIB board and an example of the settings, but the current settings on the board inside pcminn01 are as mentioned above. For more info on setting the GPIB settings refer the GPIB manual from National instruments. Neslab Chiller RTE-111D settings and control The chiller needs to be in the remote mode for computer control. Settings can be changed by the front panel buttons as described in the manual. The RS-232 port on the back of the digital controller is connected to the COM1 port of the PC with a normal RS-232 male to female cable. Serial port software settings for the chiller are : 9600 baud, 1 start bit, 8 data bits, 1 stop bit and no parity. Also the chiller only understands ascii hex characters. Use the labview vi set_temp.vi to play with the chiller temperature. The chiller needs about 2 liters of distilled water to fill and needs to be refurbished about every 36 hours or more of operation. Note: To chill below 8C (-25C to 8C) use a 50/50 mixture, by volume, of distilled water and laboratory grade ethylene glycol. Keithley 487 settings The device currently being used with the setup already has all the device settings saved as the default power ON settings. If needed to restore choose Line frequency Current limit Trigger Interval Trigger Source GPIB address 50Hz for Switzerland, 2.5mA 0.3s External 23 Connections to the backplane of 487: Current to be measured INPUT using a 3lug TriaxBNC connector Voltage to be supplied V-Source Output using BananaBNC connector GPIB connection via a GPIB cable to the computer GPIB port or any bus using the same GPIB card. Keithley 7001 Switch system and Keithley 7154 HV switching card settings The 7001 is a pretty easily configurable device. Choose cards 7154 for each slots via the front panel card configuration and the GPIB address to 07 and the rest is factory default. The 7154 HV switching cards are screw terminal cards where the connections for the apd bias and the current (i.e connections to both legs of apds, 2 per apd) are wired permanently. The current wiring of the cards in use with the gain setup has the following switch selections on the front panel when used with the new apd circuit with the line ZIF sockets. NOTE: Please carefully mount the APDs in the ZIF socket using only the PINs as shown above (1,3 5,7 13,15 17,19). If not mounted correctly the apd connections being wrong, results into junk data. From the circuit with the apds a ribbon cable connects to the screw terminals of the 7154 cards. HHigh Voltage leg of the apd (i.e the cathode) and LCurrent sensing leg of the apd. Since the G for all terminals are internally connected one need only connect any one of the GGround of the circuit. The output terminals of the 7154 cards are connected to two denuded BNC cables in the following fashion: GG and connect the junction to the G on board the 7154 output terminal. One BNC main is connected to H and the other to L. The two H BNCs are then taken out of the system and connected in a T and further connected to the Keithley 487 V-source output. And the two L BNCs are connected in a similar fashion via a T to the Keithley 487 Input using the TriaxBNC adapter. Keithley 485 and PIN monitoring Set the GPIB address to 22 and push the AutoRange button on the front panel if not already selected. GPIB address can be configured via the hardware switch on the back. Connect the input on the front panel to the appropriate lemo connector on the circuit as shown below. Also the GPIB slot at the back should be connected to the GPIB bus or the GPIB card in the computer. Temperature Sensor Analog Devices AD590 and PIN diode EG&G VTB8441B monitoring and settings The temperature sensor is mounted in the middle hole in the aluminum base plate and connections are drawn through the ribbon cable that connects on board the circuit with the 8 pin connector as shown in the figure above. The connections of the ribbon cable are described below. PIN 1 AD590 +ve PIN 3 AD590 sense PIN 4 PIN diode (VTB8441B) sense PIN 8 PIN diode (VTB8441B) +ve Calibration is needed for the AD590 it is important to ensure utmost temperature precision. Temperature sensing is done via the DAQ card using Analog Input channel ACH0 on the BNC-2090. It reads a voltage across a 10K resistor in series with the sense pin of the AD590. PIN current is measured precisely by the Keithley 485 and fed into the computer via GPIB. SOFTWARE DESCRIPTION Program location: On PC pcminn01 D:\Projects\APDs\apd_TEST_V3.vi Program Library: On PC pcminn01 D:\Projects\APDs\apd_TEST_V3.llb The program apd_TEST_V3.vi is the current version used to measure all apds for gain. It measures gain for 20 apds automatically and saves data in ascii text files on the local hard drive and also the cristal database. Typical settings on the front panel can be seen in the figure below. With these settings when the program is run first it will set the chiller to the temperature entered in Chiller Temp and waits till the temperature reading from the AD590 inside the setup is ±0.5C. Once the temperature is reached the program sets the Keithley 7001 switch to close the first position 1!1. The next step Initializes the Keithley 487 to the range for Light ON since the light curve is done first. Light is now turned ON by applying bias to the LED (currently –2.92V) and there is a waiting of 90 seconds to stabilize the light from the LED. After this the voltages from the voltage array are scanned and at each point the Current from the apd, current from PIN diode and the temperature from AD590 are plotted on the front panel. Once the light curve data is taken light is switched OFF by turning the LED bias to 0V, and a similar dark curve is taken. At the end the breakdown voltage for the apd is calculated by increasing the bias from the last point measured in steps of 0.1V till the current reaches 100µA. Gain, dM/dV are calculated and stored along with other parameters in a file G0301900001.txt at the location: D:\APD_DATA\New_apds\Lot_3_Wafer_1\25C In the directory specified (here D:\APD_DATA\New_apds\) the program creates a folder Lot_3_Wafer_1 and in this folder creates a folder 25C (and 18C when the program is run for 18C or similarly for any temperature) and stores the text file named G0301900001.txt. Apd_TEST_V3.vi Front Panel Note: For more instructions on operation please refer to the Lab Manual for the Gain setup. A typical data output file from the above settings: APD#;900003;LotNumber;WaferNumber;3;1;Date/Time;4/5/2000;9:30:57 PM;FileLocation;d:\Apd_data\New_apds\Lot_3_Wafer_1\25C\G0301900003.txt; Vr;Idark;dM/dV;MeanTemp;Vb;QEcoefficient;APDPosition;APDNumber; 350.56;10.39;3.21;25.00;395.70;0.5630;3;0301900003; Voltage;Itotal;Idark;Iphoto;Gain;dM/dV;Idark/Gain;Gain_dM/dV;Ipinlight;Ipindark;AP DStatus;new; 10.000;37.900;-0.800;38.700;1.001;-0.052;-0.799;0.999;68.700;0.000 15.000;37.900;-0.700;38.600;0.998;0.052;-0.701;0.999;68.690;0.000 20.000;38.000;-0.700;38.700;1.001;-0.052;-0.700;0.999;68.690;0.001 25.000;38.000;-0.600;38.600;0.998;0.052;-0.601;0.999;68.710;0.000 30.000;38.100;-0.600;38.700;1.001;0.000;-0.600;1.001;68.710;0.001 35.000;38.100;-0.600;38.700;1.001;0.000;-0.600;1.001;68.720;0.001 40.000;38.200;-0.500;38.700;1.001;0.000;-0.500;1.001;68.740;0.001 45.000;38.200;-0.500;38.700;1.001;-0.052;-0.500;0.999;68.720;0.001 50.000;38.200;-0.400;38.600;0.998;0.052;-0.401;0.999;68.730;0.001 55.000;38.300;-0.400;38.700;1.001;0.000;-0.400;1.001;68.750;0.001 60.000;38.300;-0.400;38.700;1.001;0.102;-0.400;1.027;68.750;0.001 110.000;40.767;0.033;40.733;1.053;0.550;0.032;1.221;68.730;0.001 160.000;54.067;0.333;53.733;1.389;1.278;0.240;2.041;68.800;0.001 210.000;105.133;0.967;104.167;2.693;1.596;0.359;4.481;68.780;0.000 260.000;244.533;2.067;242.467;6.269;1.862;0.330;11.732;68.780;0.000 310.000;669.500;4.500;665.000;17.195;2.283;0.262;18.235;68.780;0.001 315.000;750.200;4.700;745.500;19.276;2.348;0.244;20.478;68.790;0.000 320.000;843.600;5.100;838.500;21.681;2.433;0.235;23.085;68.790;0.001 325.000;952.800;5.700;947.100;24.489;2.521;0.233;26.136;68.800;0.001 330.000;1080.833;6.300;1074.533;27.784;2.622;0.227;29.733;68.810;0.000 335.000;1232.300;7.000;1225.300;31.682;2.748;0.221;34.019;68.790;0.001 340.000;1414.000;7.900;1406.100;36.357;2.901;0.217;39.200;68.800;0.001 345.000;1634.900;8.900;1626.000;42.043;3.077;0.212;45.546;68.840;0.001 350.000;1907.200;10.200;1897.000;49.050;3.261;0.208;51.573;68.810;0.001 353.000;2103.333;11.200;2092.133;54.095;3.414;0.207;57.015;68.820;0.001 356.000;2330.300;12.300;2318.000;59.935;3.596;0.205;63.352;68.810;0.001 359.000;2595.800;13.500;2582.300;66.769;3.819;0.202;70.826;68.820;0.000 362.000;2911.100;15.000;2896.100;74.883;4.079;0.200;79.763;68.820;0.000 365.000;3290.300;16.700;3273.600;84.644;4.397;0.197;90.621;68.830;0.001 368.000;3754.800;18.900;3735.900;96.597;4.806;0.196;104.101;68.860;0.001 371.000;4337.833;21.500;4316.333;111.605;5.307;0.193;121.258;68.840;0.000 374.000;5087.900;24.933;5062.967;130.911;5.951;0.190;143.741;68.850;0.000 377.000;6084.933;29.500;6055.433;156.572;6.851;0.188;174.506;68.860;0.001 380.000;7478.300;35.700;7442.600;192.440;8.138;0.186;219.198;68.850;0.000 383.000;9557.434;45.100;9512.333;245.956;10.119;0.183;289.967;68.850;0.000 386.000;12977.134;60.533;12916.600;333.978;13.527;0.181;418.993;68.860;0.001 389.000;19583.268;90.767;19492.500;504.008;0.000;0.180;0.000;68.880;0.001 Troubleshooting for Gain setup Problem Possible Reasons and Solutions 1. No good data (gain curve looks random) Check that apds are connected right, i.e right slots and the IDC ribbon connector is connected. And with light ON try to read the apd current from the keithley 487. Check the water level and add water to maintain water near high in the bath. This happens when there is already an existing file with the same name. Save in a different directory. Make sure the database file being written is not accessed from any other pc or is not too big. (>750kb) if so use a new file to store the database. Make sure the LED lemo is connected to the DAC0OUT on the BNC-2090 Possibly the current limit is exceeded. Make sure you are in the right range for expected currents for light ON and light OFF. Normally set to 20A 2. Chiller makes too much noise 3. Program stops at every apd for user intervention to replace existing file 4. Program stops saying error writing file, continue or stop 5. No light, PIN diode reads 0 even with light ON 6. The program doesn’t scan voltages till the end of the voltage table, stops somewhere before the last setting. Location of this document: On 'pcminn02' E:\Documentation of setups\Documentation for gain setup.doc CIRCUIT DIAGRAM FOR PCB USED IN GAIN SETUP Location of PCB files (binary) for this circuit on pcephc51 D:\Final circuits made by bpatel\Apd_new_1.pcb Hamamatsu APD Drawing showing the connection description for anode/cathode.