Work with Cameras on F20

Transcription

1 Chen Xu $BrandeisEM: ~emdoc-xml/en_us.iso8859-1/articles/work-with-cameras-on-f20/article.xml :19:40 xuchen Exp$ Currently, there are three cameras on our Tecnai F20 scope. They are FEI Falcon camera, Gatan Orius SC200 CCD camera and Gatan US4000 CCD camera. Falcon is a direct electron detector. Orius is a setup camera equipped with Falcon as part of the system. US4000 is transferred from Tecnai F30 on which a new Gatan K2 Summit camera system is installed. The FEI Eagle CCD camera was dismounted and returned to FEI. Due to the special properties of the new Falcon direct electron detector, some new features of Tecnai software are introduced in the newly updated Tecnai version beta. These features are mainly to protect Falcon camera sensor from over-dose irradiation. The external shutter control for various cameras is also changed from old style to a new integrated fashion. Some hardware change is also involved accordingly. In this document, I try to provide all basic information about all three cameras on the F20, both hardware and software wise. You can also get pdf version of this document here (article.pdf). Table of Contents 1 Some Properties of the Three Cameras Camera Physical Mounts and Controllers Mag & PixelSize (at specimen level) Calibration table About Dose Protector About Shutter Control with All Three Cameras A Normal Starting Up Procedure for Daily Operation Some Properties of the Three Cameras FEI Falcon Direct Electron Detector: Physical pixelsize at chip is 14µm. The viewsize is 4k X 4k. 1

2 This is a 1st generation chip, not back-thinned. This is a CMOS type, 16-bit camera. Bottom mounted, retractable by motor driven, but NOT from SerialEM. The conversion efficiency (counts per primary electron) are: 190 for 200kV and 313 for 120kV. Gatan Orius SC200 CCD camera, Model 830 2k x 2k CCD sensor Progressive interline device (2048 x 2048 pixels, 7.4µm each) 14 bit dynamic range Conversion Efficiency: ~12 counts/primary electron (120kV) Frame rate: 4x binning On-axis bottom mount, retractable Gatan US4000 CCD camera area = 4k x 4k, with a P type scintillator facing electron pixelsize on chip = 15µm 4-port readout Conversion efficiency: ~ 14 counts/primary electron at 300kV, ~22 at 200kV and at 120kV. Dynamic range: 16 bit Bottom mounted, retractable 2 Camera Physical Mounts and Controllers Here is a picture showing how three cameras are mounted on-axis after viewing chamber. 2

3 FEI Falcon direct detctor and Gatan US4000 CCD are mounted in head-to-head configuration. And Gatan US4000 CCD is mounted right below the housing piece for Falcon and Orius. Therefore, all three cameras are on-axis and retractable. Below is a picture showing all camera controllers and an FEI Central Shutter Unit (CSU). 3

4 The CSU is a centralized controller starting to appears with Titan. As FEI Falcon camera is retrofitted to our Tecnai F20, we also get this unit. All the shutter signals from each cameras controllers are input to this unit and the unit sends out shutter signals to microscope through a single pair of BNC cables. TIA has to be started up before this shutter control unit works properly. 3 Mag & PixelSize (at specimen level) Calibration table The calibration was done using standard 0.463µm distance grating grid and <001> oriented Au crystalline standard specimen. It is obtained using an FEI software "MagCal". It measures pixelsizes at each and all the magnifications for one camera and interpolates values for rest two cameras. These calibrated values are believed to be accurate enough for SerialEM automation and normal usage. If you have concern about the accuracy for one specific magnification for high resolution sturcture purpose, it is recommended to double check it using special standard specimen such as TMV or Tropomyosin Para-crytals. The mag and pixelsize information in the table here is mainly for reference purpose. The images taken by either Tecnai/TIA, Gatan DigitalMicrograph(DM) and SerialEM have this info embedded in the images already. Index_Mag Mag_ScreenDown(X)Mag_ScreenUp(X) Pixelsize(nm) - Orius(7.4µm, 2kX2k) US4000(15µm, 4kX4k)

5 Index_Mag Mag_ScreenDown(X)Mag_ScreenUp(X) Pixelsize(nm) - Orius(7.4µm, 2kX2k) Work with Cameras on F20 US4000(15µm, 4kX4k)

6 4 About Dose Protector In order to prevent Falcon chip from over-dose irradiation, Tecnai introduces a new software component called "Dose Protector". Every time when you start up TIA interface, you will have to calibrate a beam intensity before you can use Falcon camera. Otherwise, the beam gets planked as long as Falcon camera is in inserted position. For an user, only beam intensity is to be calibrated. Other system calibrations such as relative intensities for different spot size etc. should be done by Supervisor already. The calibration is done for each pair of Gun Lens and Extracting Voltage. Calibrating the beam intensity is rather simple, you follow a three-step instruction and then you are done. As hinted above, if you don t plan to use the Falcon camera for your session, you can skip it. Note: There are some system-wise calibrations beside the one done by an user after starting TIA. Those calibrations are done by Supervisor and are needed to be done for combinations of each Gun Lens and Extracting Voltage that one wants to use. The protection from Dose Protector is very robust. It acts at TEMserver level. For example, before you calibrate the dose intensity or your beam intensity is out of the calibration range, you can not get an image from Falcon camera. If you do insert Falcon camera and try to take an image using SerialEM, you will get a timeout error message rather than getting a blanked image. This is very good, as we won t have worry about possible damage from using the third party software - SerialEM! 5 About Shutter Control with All Three Cameras In the past, Gatan camera controls shutter by directly sending 5V signal to gun tilt coil or/and projector lens coil. This is no longer the case anymore. Instead, all the shutter cables from camera controllers go to Central Shutter Unit (CSU) to which FEI Tecnai has total control. It might not sound anything troublesome. However, it results in a freedom loss at selecting camera via non-fei software interface. For example, you can still select different camera from Gatan DM interface, but imaging from Gatan interface won t have proper control to shutter. You can get an image, but the image is not right. The same thing happens to SerialEM, you can get image, but the image might not be good. The only way to get shutter control correct is to also select the same camera from FEI TUI Camera camera list. This makes freely switching camera in scripting (macro) command impossible. 6 A Normal Starting Up Procedure for Daily Operation Log into F20 Tecnai Computer. Start interfaces in order : Tecnai User Interface(TUI) DigitalMicrogaph TIA. Select "Falcon" from camera list in TUI, then Start up SerialEM. 6