  Local Alfven wave (LAW) resonances are excited in tokamak plasmas by an
externally driven electro-magnetic field, with the frequency below the ion
cyclotron frequency, where using of the Alfven waves is assumed. Recently, wave
driven density fluctuations at the LAW resonance m=+/-1, N=+/-2 with few kW
power deposition and 4 MHz frequency were detected in TCABR (Bt =1.1T, q0 =1.1,
n0=1.4-2.0 10^{19}/ m^3) using a fixed frequency (32.4GHz) O-mode
reflectometer. Here, we show that combination of small power deposition in LAW
resonances, swept by plasma density variation or scanned with generator
frequencies, in combination with detection of the density fluctuations in the
LAW resonances by reflectometry can serve as diagnostic tool for identification
of the effective ion mass number Aef and q-profile in tokamaks. The idea is
based on the simultaneous detection of the position of m=+/-1 local AW
resonances, which are excited by M/N=+/-1/+/-2 antenna modes, and m=0 generated
by poloidal mode coupling effect in tokamaks. According to LAW dispersion, the
m=0 resonance depends only on the effective ion mass number and does not depend
on the q-profile. Then, using these data we can define q-value at the position
of m=+/-1 L AW resonances. Using TAE coils with even toroidal modes (N=2, 4,..)
and AW generator in the frequency band 0.6-1 MHz, an application of this method
to Joint European Torus (Bt=2.3T, q0 =1-1.3, n0=5-7 10^19/m^3) is demonstrated.
