OPERATION OF THE PHILIPS CM-200 TRANSMISSION ELECTRON MICROSCOPE

by Birute Jakstys and Anna Klintsova (2nd revision, 01/2003). When not in use, the CM-200 should be in the MICROSCOPE ON (see 1. below) configuration with the HIGH TENSION OFF. The microscope is normally never turned off.

Please record your name, other requested specifics, and comments in the logbook.

ITG users may reserve time on the TEM using the TEM calendar.

Initiating Operation:	When the CM-200 is ON, the white STAND BY and red MICROSCOPE OFF buttons will be illuminated; the ON button will be dark. The lit buttons indicate their availability as emergency functions while the microscope is running. Depress the PANEL DIM knob to illuminate the data monitor screen and emission gauge. Clockwise rotation of this knob increases the intensity of the panel lighting and the light on the flexible stalk. Clockwise rotation of the DATA DIM knob increases the brightness of the data monitor screen. Ensure that the UHV and HIVAC indicator lights are lit (green). [See 7. below if the two indicator lights are not lit.] (Anticontamination Device) Place the metal-clad glass vacuum dewar into its holder to the right of the column so that the soft copper wire "beard" hangs inside it. The glass viewing windows should be covered for safety. Fill the dewar nearly full with liquid nitrogen and place the styrofoam cap on top. The data monitor screen will display the CM-200 PHILIPS MICROSCOPE STATUS startup page or, more likely, one of the MODES or MODE SELECTION pages. If the READY light (on the pushbutton directly below the data monitor screen, to the right) is lit, pressing it will move the screen selection back in the hierarchy of pages. Press the MODES key to obtain the MODE SELECTION page. Press the TEM LOW DOSE key on the MODE SELECTION page. [Unless we are taking film negatives, we now use the 'scope almost exclusively in TEM LOW DOSE BRIGHTFIELD mode, with SEARCH selected. This is because the TVIPS digital imaging software was written to be operated in this mode.] If the letters TEM LOW DOSE are highlighted it will be necessary to press only once; otherwise press the TEM LOW DOSE key twice. The screen should now display the TEM LOW DOSE BRIGHTFIELD page. Press the VACUUM key to check the vacuum status of the instrument. It should read READY at the top center of the data monitor screen. If it reads START-UP the operator must wait for the vacuum to improve before the 'scope can be used. [If you find the microscope stuck at START-UP, e.g., if (on the VACUUM page) P3 reads less than 63 but IGP is at 0 (in this case indicating that the ion getter pump is off) and the IGP icon is not highlighted on the schematic, press VACUUM SYSTEM OFF, wait a second or two, and then press VACUUM SYSTEM ON.] Do not use the microscope unless the ion getter pump (IGP) reading is lower than 20. To return to the TEM LOW DOSE BRIGHTFIELD page press the READY button. To select the operating voltage, press the PARAMETERS key to open the PARAMETERS pages. On the first of these pages the kV may be modified by pressing the left (lower) or right (higher) key adjacent to the HIGH TENSION kV notation on the screen. Most TEM users in this laboratory work at 120 kV. Also on the first PARAMETERS page is the EMISSION setting, which should ordinarily be left at 1. A higher value will produce a brighter beam image but will also shorten the lanthanum hexaboride (LaB₆) filament life. Press the READY button to return to the TEM LOW DOSE BRIGHTFIELD page. Press the HIGH TENSION ON/OFF button (illuminates green when the high tension is on). With the high tension on, an operator may load previously stored or default alignment/mode/stigmator settings for the kV at which the 'scope is operating. This requires logging onto the computer (the one with the keyboard and mouse on the movable rest and the CRT on top of the control panel), opening TCL from QuickFind, in the Start menu, and accessing the EM MENU window (F4). At this point, you may select ALIGNMENTS from the EM MENU window and load previously stored settings. IMPORTANT: If you intend to expose TEM negatives using the built-in camera, the CCD camera control unit, on top of the instrument panel just to the left of the column, must be switched to CM rather than CCD. Otherwise the beam blank will remain on and EXPOSURES WILL NOT BE MADE. Because we are now using the CCD camera almost exclusively, film exposure/processing is not covered in this set of instructions.
Beam Alignment:	These functions are performed either without a specimen holder or with the specimen holder inserted fully into the 'scope but held just out of the electron beam by wedging a pen or pencil vertically between the specimen holder handle and the face of the Compustage. If a specimen holder is not in place, a radiation safety interlock keeps the spot size at 5 or a higher number (indicating a smaller spot size; the largest and brightest spot size is 1). The interlock prevents a larger spot size from being selected and produces a much dimmer beam than that seen with the holder in place. Note: A specimen holder (without a specimen or with a specimen but wedged just out of the electron beam) must be in place in order to adjust the C2 (COND) stigmator (8. in the list below). Using the MAGNIFICATION knob, select 17,500x. Press the MODES key to access the MODE SELECTION page. From there, press CONFIGURATION. The CONFIGURATION page displays the filament heating status and provides a schematic of the available apertures (aperture memo) for the condensor 2 (C2), objective, and selected area lenses. Under CATHODE, at the top of the page, LaB6 should be highlighted, indicating that a LaB₆ filament is in use. filament should be highlighted next to the number (usually between 22 and 30) indicating the saturation limit of the filament. With the limit set (highlighted), the operator can turn the FILAMENT knob clockwise indefinitely without fear of oversaturating the filament. Turn the filament up to a number that is 4 or 5 less than the indicated filament limit. Defocus the electron beam by turning the INTENSITY knob clockwise to strongly overfocus the C2 lens. Bring the beam back to crossover (the smallest image of the beam) and center it using the SHIFT X/Y knobs Choose a C2 aperture (usually position 3, which is a 100-micron aperture) by rotating the largest knurled knob on the topmost aperture control on the column to the desired position. Using the INTENSITY knob, slowly overfocus (turn clockwise) the beam to coincide with the diameter of the intermediate-sized black circle on the phosphorescent viewing screen. If the defocused beam is not coincident with the circle, adjust it using the C2 aperture centering controls. These are both the intermediate-sized knurled knob on the aperture rod and the knurled knob on the side of the assembly (to the right). DO NOT TWIST THE SMALLEST, INNERMOST KNOB (WHICH IS NOT KNURLED) BECAUSE IT UNSCREWS THE APERTURE ROD. Repeat these steps (3 and 5) until the beam spreads uniformly around the reference circle while being overfocused (INTENSITY knob). Using the INTENSITY knob, adjust the beam to crossover. Depress the FINE button (to the left of the INTENSITY knob; the indicator light turns green when it is on) and use the INTENSITY knob to sharpen the desaturated filament image. Center the image using the SHIFT X/Y knobs. Press the STIG button, on the right-hand instrument panel, to open the STIGMATOR CONTROL page. Press the COND key on the data monitor screen to select the C2 lens for astigmatism correction. Use the MULTIFUNCTION X/Y knobs, while rotating the beam through crossover using the INTENSITY knob, to obtain the cleanest, roundest desaturated filament image possible. [If a tungsten instead of a LaB₆filament was in the 'scope, this is where the desaturated filament image would appear like a central bright spot with a halo around it, similar to the CBS TV logo.] Press the STIG button to return to the CONFIGURATION page. Turn the FILAMENT knob clockwise to fully saturate the filament. When the saturation point (as defined by the FIL LIMIT) has been reached, the microscope will emit a 'beep.' Press the READY button and then the TEM LOW DOSE key to return to the TEM LOW DOSE BRIGHTFIELD page. Using the lever to the left of the viewing chamber, lower the small phosphorescent screen into place. Insert the beam stop (at the right-hand side top of the viewing chamber) so that it will be visible across the small screen. Use the binoculars to observe the beam stop. To adjust the binoculars for your eyes, first adjust the interpupillary distance so that you can see through them with both eyes; then adjust each eyepiece so that the rough edges of the beam stop are in focus for each eye. When you are done, retract the beam stop and lift the small screen back out of view.
Specimen Holder Removal, Loading, and Insertion:	Never remove or insert the specimen holder when the red indicator light (on the front of the compustage housing) is on. Do not touch the leading edge of the specimen holder (from the o-ring to the tip) with ungloved hands. This portion resides inside the vacuum and must be kept clean. REMOVAL: To remove the specimen holder from the column, carefully pull the round black handle straight out until it stops, and hold it firmly so that it does not get pulled back into the 'scope by the vacuum. Now rotate it clockwise until it stops again; it may now be pulled straight out (carefully), free of the column. The specimen holder should be set down only on its Lucite stand. SPECIMEN LOADING: Use the pin tool (located in the Lucite stand, under the tip) to lift the grid clamping device at the tip of the speciment holder. Transfer your grid to the specimen holder using forceps. To make scanning the grid easier, you may wish to orient one set of grid bars parallel to the long axis of the specimen holder. Use the pin tool to carefully lower the clamping device onto the grid and lock it in place. INSERTING THE SPECIMEN HOLDER INTO THE COMPUSTAGE: With the small pin on its shaft at the 4 o'clock position, carefully insert the specimen holder into the airlock entryway at the center of the compustage. Insertion of the holder will initiate the prepumping sequence, and the red indicator light on the front of the compustage will come on. Slide the holder in until it stops and feels fairly solid to the touch; at this point it will not go all the way in. The data monitor screen will automatically open to the HOLDER SELECTION PAGE. Press the appropriate key (in most cases you'll choose NO COMPUSTAGE B TILT) and then press the READY button (below the data monitor screen). The data monitor screen will return to the previously selected page (normally TEM LOW DOSE BRIGHTFIELD). After the red indicator light goes out, grip the specimen holder firmly by its black plastic handle and rotate it counterclockwise. When it reaches the limit of its rotation, the vacuum will begin to pull the holder deeper into the column. Maintain a firm grip on the handle as the holder enters the column so that it does not get drawn in too quickly. Once the holder appears to be all the way in, jiggle it very gently to ensure that it is indeed inserted completely into the column.
Eucentric Height Adjustment:	Set the magnification to 5,800x and use the X/Y JOYSTICK to center a small notable feature of your specimen. Focus your chosen feature using the knobs marked STEP SIZE. The outer knob changes the focus; the inner knob (the step size adjustment) modifies the amount of focus change per 'click' of the outer knob. From the TEM LOW DOSE BRIGHTFIELD page, press COMPUSTAGE once; the COMPUSTAGE REGISTER CONTROL page will appear. Press A-WOBBLER; this will initiate back-and-forth tilting of the goniometer. Use the Z control lever on the JOYSTICK to move the specimen up or down, whichever is appropriate to minimize apparent movement of the centered feature. When the feature moves only minimally or not at all, press the A-WOBBLER key to inactivate tilting; then press the READY button to return to TEM LOW DOSE BRIGHTFIELD.
Pivot Point Alignment:	Ensure that the specimen is eucentric before performing this procedure. For this procedure you may work with the OBJECTIVE APERTURE in place to protect your specimen. Center (X/Y JOYSTICK) and focus (concentric knobs under STEP SIZE) an image feature at 24,500x (MAG knob). Press the ALGN button to access the ALIGNMENT SELECTION page. Note that the alignments are divided into PROCEDURES (on the left side of the page) and DIRECT alignments (most of which are on the right side of the page). Most users will not want to access the PROCEDURES, which are long and complicated. For this set of instructions we will be using only the DIRECT alignments. Using the INTENSITY knob, adjust the beam to crossover. Press the beamcoils PIVOT POINT X key, on the right side of the page, so that it is highlighted. Using the MULTIFUNCTION X/Y knobs, bring the two beam spots (the pivot points, on the phosphorescent viewing screen) together so that they overlap. Center the coinciding spots using the SHIFT X/Y knobs. Press the beamcoils PIVOT POINT Y key. Using the MULTIFUNCTION X/Y knobs, bring the two beam spots together so that they overlap. Center the coinciding spots using the SHIFT X/Y knobs. Press the ALGN button to exit the ALIGNMENT SELECTION page.
Rotation Center Alignment:	This procedure may be performed with the OBJECTIVE APERTURE in place to protect the specimen and add contrast to the image. Focus and center a feature of the specimen at 100,000x. Press ALGN to open the ALIGNMENT SELECTION page. On the upper right-hand side of the page, press ROT CENTER so that it becomes highlighted. Now either voltage or current centering may be performed; it is not necessary to do both. VOLTAGE CENTERING: On the lower right-hand side of the page, select VOLT (under rot center VOLT CURR) so that it becomes highlighted. This will cause the high tension to modulate (the inner STEP SIZE knob adjusts the amplitude of modulation). If the chosen feature shifts off center laterally, the beam is not aligned along the optical axis of the microscope and must be corrected. Use the MULTIFUNCTION X/Y knobs to stabilize the feature at the center of the screen, eliminating all lateral movement. The feature should appear to be pulsating. Press the ALGN button to return to the TEM LOW DOSE BRIGHTFIELD page. CURRENT CENTERING: On the lower right-hand side of the page, select CURR (under rot center VOLT CURR) so that it becomes highlighted. This will cause the objective lens current to modulate (the inner STEP SIZE knob adjusts the amplitude of modulation). If the chosen feature shifts off center laterally, the beam is not aligned along the optical axis of the microscope and must be corrected. Use the MULTIFUNCTION X/Y knobs to stabilize the feature at the center of the screen, eliminating all lateral movement. The feature should appear to be pulsating. Press the ALGN button to return to the TEM LOW DOSE BRIGHTFIELD page.
Centering the Objective Lens Aperture:	For this procedure a specimen must be in place. Choose an area for which it is acceptable to sustain beam damage. With the OBJECTIVE APERTURE out, set the magnification to 5,800x and overfocus the beam by turning the INTENSITY knob clockwise from crossover. Set the focus step size (inner STEP SIZE knob) to 5 and press the D button to put the 'scope in diffraction mode. If necessary, adjust the camera length to 620 mm using the MAG knob. [Note that you can accidentally choose 6.2 m rather than 620 mm.] Center the diffraction spot using the MULTIFUNCTION X/Y knobs. Using the focus (outer STEP SIZE) knob, refocus the beam to the smallest, brightest spot. It may also be necessary to adjust the INTENSITY knob.. Insert the OBJECTIVE APERTURE by rotating the aperture displacement lever below it to the left. Apertures may be selected by rotating the largest knurled knob on the objective aperture assembly to any one of four numbered positions. (The APERTURE MEMO lists the diameters and positions of the apertures currently installed in the 'scope. It may be accessed from the TEM LOW DOSE BRIGHTFIELD page by clicking MODES and then CONFIGURATION.) Once the aperture has been selected, center it using both the smaller knurled knob in the series on the aperture assembly and the small knurled knob to the right. Remember not to manipulate the smallest, innermost knob, which is not knurled and will unscrew the aperture rod. Press D to exit diffraction mode.
Objective Lens Astigmatism Correction:	Select an area that may be imaged at high magnification without harming any desirable portions of the specimen. Increase the magnification to 175,000x or higher and adjust the illumination so that the substructure or background grain of the specimen may be observed easily. The INTENSITY will have to be modified and the beam will have to be recentered using the SHIFT X/Y knobs (Deflectors) as the magnification is increased. This latter function may alternatively be controlled using the RST button, on the panel to the left of the column.< Set the focus step size to 2 and obtain a slightly underfocused image for maximum contrast. Press the STIG button to open the STIGMATOR CONTROL page. If it is not already highlighted, press the OBJ key on this page. Use the MULTIFUNCTION X/Y knobs, one at a time, to obtain the sharpest possible image of the grain substructure. Confirm that any astigmatism has been corrected by varying the focus (back and forth through focus, from underfocus to overfocus) and watching to see if a "streaking" pattern emerges and changes direction between under- and overfocus. If the astigmatism has been corrected, the specimen will vary only in focus, with no pattern evident. Repeat steps 4 and 5 until this state is achieved. Press the STIG button again to return to the TEM LOW DOSE BRIGHTFIELD page.

Sponsors: National Science Foundation BIR-9317781