Chapter 2. CP/MAS Solids Operation
17
VNMR 6.1C User Guide: Solid-State NMR 01-999162-00 C0402
Full-Solids
1
H/
19
F 1 kW Amplifiers
UNITY
INOVA, UNITYplus, and UNITY wide bore systems can be equipped with the full bay
solids option that includes a 1 kW
1
H/
19
F amplifier. The amplifier is a class AB tube
amplifier, tunable to either
1
H or
19
F, driven by the standard 50 W high band amplifier, and
produces 1 kW at 400 MHz and below. Power output at 500 to 900 MHz is lower and
specifications are available for individual amplifiers.
Cavity tuned amplifiers used in older systems are distinguished from the current amplifiers
by the external control box used to tune the cavity. These older amplifiers are often referred
to as CPI amplifiers in recognition of the manufacturer of the tube.
Current and newer systems incorporate the CMA amplifier manufactured in Fort Collins,
Colorado, USA by Varian Inc. These amplifiers offer the option of either class AB or class
C operation. CMA amplifiers are tuned manually using calibrated tuning knobs. The
amplifier is enabled or disabled using the switches on the front panel of the full solids bay.
• Enable high power amplifier operation
Place the
HI BAND amplifier switch in the HI POWER position (an orange LED will
illuminate) and enable high power with the silver button (a green LED will illuminate).
• Disable high power amplifier operation
Place the
HI BAND amplifier switch in the LO POWER position and press the red
button. The 50 W amplifier remains enabled.
CPI and CMA amplifiers operate in both pulsed and continuous (CW) modes. The
parameter ampmode is used to select the operation mode for CPI amplifiers. When the
parameter ampmode is not present the amplifier is set in the default CW mode (
ampmode
=
‘c’
or
‘d’
) which is correct for CP/MAS experiments. CMA amplifier modes;
CLASS C, CLASS AB (CW), or GATE ACTIVE (pulsed), are selected using the three
position switch on the front panel of the amplifier. Set the switch to
CLASS AB mode for
CP/MAS experiments,
GATE ACTIVE mode for
1
H or
19
F observe, or CLASS C for special
multipulse experiments. The ampmode parameter must be either set to the correct value or
in the default mode as it determines the operation of the 50 W
1
H/
19
F amplifier that drives
the CMA amplifier.
Full-Solids Lowband 1 kW Amplifiers
The high power lowband amplifier in the full solids bay is a class A linear amplifier and is
either an AMT 3201 (older systems) or AMT 3200 series amplifier. These amplifiers
produce 1 kW at full power over a range of 6 to 220 MHz (up to
31
P for systems with
1
H at
500 MHz or
13
C for systems with
1
H at 900 MHz).
The 3201 amplifier on older systems does not have a power meter on the front panel. Input
to the older amplifier is from the standard 300 W lowband amplifier in the console. The
high power amplifier is enabled or disabled using the switches on the front panel of the full
solids bay.
• Enable high power amplifier operation
Place the
LO BAND amplifier switch in the HI POWER position (an orange LED will
illuminate) and enable high power with the silver button.
• Disable the high power amplifier and return to the standard amplifier
Place
LO BAND amplifier switch in the LO POWER position and press the red button.
The 300 W amplifier remains enabled.
The 3200 amplifier on newer systems has a power meter on the front panel. Input drive is
provided by the milliwatt transmitter board in the console. The high power amplifier is
enabled or disable using the switches on the front panel of the full solids bay.
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