Vacuum chamber, ion source

In the continuum flow regime the mean free path X is much smaller than the orifice diameter, and the exit pressure from the reactor is orders of magnitude greater than the backing pressure in the ion source vacuum chamber. The Mach number is unity that is, the flow speed, t , through the orifice is sonic ... 

Fig. 3. Schematic drawing of the molecular beam apparatus. The labeled parts are (/) heated oven source, (2) source vacuum chamber, (i) source differential vacuum chamber, (4) main vacuum chamber, (5) crossing point of the laser beam with the molecular beam. (d> electroo bombardment ionizer, (7) quadrupole mass spectrometer and (8) Daly ion detector.

Vacuum-lock inlet. An inlet through which a sample is first placed in a chamber the chamber is then pumped out, and a valve is opened so that the sample can be introduced to the mass spectrometer ion source. A vacuum-lock inlet commonly uses a direct-inlet probe, which passes through one or more sliding seals, although other kinds of vacuum-lock inlets are also used. 

In the magnetic-sector instrument (Figure 1.1), gas phase ions produced in the ion source by one of several different methods are accelerated from near rest (thermal energy) through a potential gradient (commonly kV). These ions travel through a vacuum chamber into a magnetic field at a... 

As an electrolyte, Nafion 112 (Du Pont, Inc) membrane was pretreated using H2O2, H2SO4 and deionized water before ion beam bombardment. The prepared membranes with a size of 8 X 8 cm were mounted on a bombardment frame with a window size of 5 x 5 cm, equal to the active area of the test fuel cells, and dried up at 80 C for 2 hr. Then, the mounted membrane was brought in a vacuum chamber equipped with a hollow cathode ion beam source as described in the previous study [1]. Ion dose was measured using a Faraday cup. Ion density... 

The chemical compositions of the isolated Au SR clusters were investigated by mass spectrometry [15,16,18, 22,32-35]. TEM was used to confirm that the species detected by the mass spectrometer represents the clusters in the sample. Figure 3a is a schematic representation of the top view of the mass spectrometer, which consists of five stages of differentially pumped vacuum chambers. The apparatus accommodates two t5 pes of ion sources, electrospray ionization (ESI) and laser-desorption ionization (EDI), and a time-of-flight (TOE) mass spectrometer with a reflectron. Details of the apparatus and the measurement protocols are described below. 

Figure 4.2 is a block diagram that illustrates the principle of the SIMS technique. The apparatus includes a primary ion source, a vacuum chamber where the objects under study are placed, a mass analyser and a secondary ion detector. 

Fig. 1.3. Experimental setup for electrochemical thermal desorption mass spectroscopy (ECTDMS). C = electrochemical cell, W = working electrode, El = electrolyte inlet, EO = electrolyte outlet, EH = electrode holder, V = valve, TP = turbo pump, VC = vacuum chamber, L = light source, W = window, P = protective jacket, A = aperture to analysis chamber, GI = grid ion source, S = SEM detector.

The solution to be electrosprayed is passed through the electrospray capillary (ESC) by means of a motor driven syringe. Some of the spray containing the ions then enters the pressure reducing capillary (PRC) leading to the forechamber (FCH) of the ion source. The exit tip of the PRC directs the gas jet in a direction parallel to the bottom of the FCH, i.e. across the interface plate (IN). An orifice of 4 mm diameter in the interface plate connects the FCH to the reaction chamber (RCH). The ions in the jet exiting from the PRC are deflected out of the jet towards this orifice and into the RCH by means of an electric field applied across the FCH. A weak field is also applied across the RCH. At the bottom of the RCH a small orifice, 100 pm diameter, allowed some gas and ions to leak into the vacuum of the mass... 

Example The vacuum system of non-benchtop mass spectrometers consists of one to three rotary vane pumps and two or three turbo pumps. Rotary vane pumps are used for the inlet system(s) and as backing pumps for the turbo pumps. One turbo pump is mounted to the ion source housing, another one or two are operated at the analyzer. Thereby, a differentially pumped system is provided where local changes in pressure, e.g., from reagent gas in Cl or collision gas in CID, do not have a noteworthy effect on the whole vacuum chamber. 

In atmospheric pressure chemical ionization (APCI) ion-molecule reactions occurring at atmospheric pressure are employed to generate the ions, i.e., it represents a high-pressure version of conventional chemical ionization (Cl, Chap. 7). The Cl plasma is maintained by a corona discharge between a needle and the spray chamber serving as the counter electrode. The ions are transferred into the mass analyzer by use of the same type of vacuum interface as employed in ESI. Therefore, ESI ion sources can easily be switched to APCI instead of an ESI sprayer, a unit comprising a heated pneumatic nebulizer and the spray chamber with the needle electrode are put in front of the orifice, while the atmospheric pressure-to-vacuum interface remains unchanged. [48,138]... 

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