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hv_bias [2014/11/19 11:53]
pereira [Object Scintillator] |
hv_bias [2023/10/17 09:40] (current)
noji |
| ====== Detector bias control ====== | ====== Detector bias control ====== |
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| | ===== HV Remote control ===== |
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| ===== General Information ===== | The high-voltage of the plastic scintillator and the MCP at Object, the [[Detectors#Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPACs]] at Intermediate Image, the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]], [[Detectors#Ionization Chamber|ion chamber]], [[Detectors#Plastic scintillators|plastic scintillator]], and [[Detectors#Hodoscope|hodoscope]] at Focal Plane are remotely controlled via CS-Studio Phoebus (see figure below). |
| The high-voltage of the [[Detectors#Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPACs]], [[Detectors#Ionization Chamber|Ion Chamber]], the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]], [[Detectors#Plastic scintillators|FP Scintillator]], and [[Detectors#Hodoscope|Hodoscope]] are remotely controlled via GUI control panel (see figure below). The GUI can be opened from the desktop of the u6pc5 control computer. This application allows also to set a maximum limit in the detector current. The voltages of these detectors depend on the Z of the fragments to be measured and their energy. The figure below shows the HV GUI during experiment e10002, which used Si-26 and Al-25 fragments at around 115 MeV/u. These voltages can be used as a reference before starting an experiment. However, the final values will have to be modified during the beam tuning in order to optimize the performance of the detectors. It is convenient to verify the reference values with D. Bazin. | |
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| {{:wiki:hv-gui.png?700|GUI control panel of the S800 detectors HV}} | {{:wiki:phoebus_diag_hv.png|CS-Studio Phoebus DIAG HV control}} |
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| | This “S800 HV Bias Power Supply” page is linked from both "S800" and “DIAG” launchers, a screenshot of the former of which is shown below. |
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| | {{:wiki:css_s800launcher_hv.png|}} |
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| detectors | The ramp rate can be changed in the "Details". ISEG cards that are used here have only one ramp rate per bank of channels, so changing the rate for one channels will change the rate for all the others in the same bank. When you ramp the HV, ensure that the ramp rate is set properly. |
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| [[Detectors#Tracking Parallel Plate Avalanche Counters (TPPAC)|TPPACs]], the [[Detectors#Ionization Chamber|Ion Chamber]], and the [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDCs]] have ISEG power supplies run through a single VME-based bias control. The computer interface for this bias control -- the S800 Detector HV Control -- is typically run on the **devop1** computer in data-U6 and is started by clicking on **S800 HV** under the Operations option on the taskbar. The [[Detectors#Plastic scintillators|Object scintillator]] and the [[Detectors#Plastic scintillators|FP Scintillator]] are each controlled separately as described below under the sections for each detector. | Each channel can also be accessed from by going to “FRIB EXP” -> “Power Supplies” and open the “EXP-S3” tab, which looks like the screenshot below. |
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| | {{:wiki:phoebus_ps_main.png|CS-Studio Phoebus PS HV control}} |
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| | The actual HV modules are located on the top level of the S3 vault, under the FP chamber. |
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| ===== | {{:wiki:img_1369.png|}} |
| Apart from the detectors listed above, the voltages of the object scintillator and the electrostatic gate of the CRDCs are adjusted manually. | |
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| The bias for the object scintillator is controlled via the H.V. power supply {{:wiki:Manual_Canberra_HV_3002D.pdf|Canberra model 3002 D}} located in the crate to the right of the data-U6 (see figure below). The voltage will be adjusted at the beginning of the experiment. This scintillator has to be turned off or put on "standby" when entering the vault due to its sensitivity to light. | Other examples of HV values used with different fragment beams are: |
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| In order for the CRDCs to work, it is necessary to bias their electrostatic gate. This is done via the H.V. Tennelec power supply located on the left side of the object-scintillator Canberra power supply (see figure below). | |
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| {{:wiki:nim-crate2-du6.jpg?400|NIM crate 2 in data-U6}} | |
| ===== FP Scintillators ===== | |
| Only the fist two scintillators are typically used since in most cases particles do not reach beyond the second detector. The biases for the anode and the drift electrode are each controlled separately via the S800 Detector HV Control. To protect the scintillator PMT bases from damage from discharge under poor vacuum conditions (for example, during a window break on one of the nearby gas detectors), the 12-Volt supply for the PMT bases is interlocked to switch off if the pressure in the focal plane box rises above some minimum value as read by an ion gauge. The ion gauge controller (a black box with an LED digital display) is mounted on the south support structure for the focal plane chamber. The interlock condition is communicated to the PMT bias supply via a multi-pin “D” connector on the back of the controller. If the ion gauge is off, the interlock condition prevents biasing of the scintillator. It is possible to manually override the interlock condition for testing by connecting a “cheater” connector in place of the ion gauge controller to the cable for the interlock. | |
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| ===== Ion Chamber ===== | |
| The biases for the anode and the drift electrode are each controlled separately via the S800 Detector HV Control. Parts of this detector rely on the same 12-Volt power supply used to power the bases of the FP Scintillator PMTs. If the vacuum-based interlock condition for protecting the FP Scintillator PMTs is triggered, the 12-Volt power supply will not be available for the Ion Chamber. | |
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| ===== CRDCs ===== | |
| Each of the two detectors, CRDC1 and CRDC2, has a separate bias control for the anode and the drift electrode via the S800 Detector HV Control. Please keep in mind that a change in the drift voltage of the CRDCs strongly affects the drift velocity of the electrons and a new mask calibration has to be done to be able to determine the y position of particles. Apart from the CRDCs, it is important to bias the electrostatic gate (see section [[Detectors#Cathode Readout Drift Chambers (CRDC)|CRDC]]). The power supply is located in the crate to the right of the data-U6; the typical voltage is 26 V. | |
| ===== TPPACs ===== | |
| The bias of each of the two detectors, PPAC1 and PPAC2 is controlled individually via the S800 Detector HV Control. There are two types of detectors used for the TPPACs: either the “classic” PPACs or [[Detectors#Tracking Parallel Plate Avalanche Counters (TPPAC)|multi-strip PPACs]] with individual strip readouts for handling higher rates. There is not a difference between the two detector types in terms of how the data is used. They do differ in terms of electronics and acquisition. | |
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| | * **CRDC1 and CRDC2**: |
| | * For He-3 @ ~130 MeV/u: CRDC1 (Anode=1120 V, Drift=1000 V); CRDC2 (Anode=1120 V; Drift=1000 V) |
| | * For Be-12 @ ~30 MeV/u: CRDC1 (Anode=970 V, Drift=1000 V); CRDC2 (Anode=970 V; Drift=1000 V) |
| | * For Ar-34 @ ~80 MeV/u: CRDC1 (Anode=860 V, Drift=1000 V); CRDC2 (Anode=840 V; Drift=1000 V) |
| | * For Zn-58 @ ~44 MeV/u: CRDC1 (Anode=740 V, Drift=1000 V); CRDC2 (Anode=740 V; Drift=1000 V) |
| | * For Rb-74 @ ~40 MeV/u: CRDC1 (Anode=650 V, Drift=1000 V); CRDC2 (Anode=650 V; Drift=1000 V) |
| | * For U-238 (88+) @ ~70 MeV/u: CRDC1 (Anode=570 V, Drift=1000 V); CRDC2 (Anode=570 V; Drift=1000 V) |
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| | * **FP scintillator (E1 up and E1 down)**: |
| | * For He-3 @ ~130 MeV/u: UP (1790 V); DOWN (1760 V) |
| | * For Be-12 @ ~30 MeV/u: UP (1770 V); DOWN (1700 V) |
| | * For Ar-34 @ ~80 MeV/u: UP (1580 V); DOWN (1510 V) |
| | * For Zn-58 @ ~44 MeV/u: UP (1400 V); DOWN (1340 V) |
| | * For U-238 (88+) @ ~70 MeV/u: UP (1180 V); DOWN (1280 V) |
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| | * **IC**: |
| | * Typically 200 V |
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