Stelar Magnetic Relaxation Tracer


SMARtracerTM is an innovative, cost-effective, bench-top Field Cycling NMR instrument designed to measure Magnetic Relaxations as a function of magnetic field strength.

No other conventional Time Domain NMR instrument can produce such information.

SMARtracer is the ideal, cost-effective instrument to exploit in clinical and industrial applications the high quan- tity of information content in theNMRD profiles acquired by means of the Field Cycling NMR relaxometry techniques.

In fact, the most pronounced relaxation phenomena in ter- ms of field dependence of T1 and T2 are expected at relati- vely low magnetic field, where the low-frequency molecular motions may have a large influence on the NMR relaxation. This is particular apparent with longitudinal relaxation time T1. This information cannot be obtained with any other TD (Time Domain) LR (Low resolution) NMR instrument.


Relaxation times

Measurement of relaxation times from a fraction of a millisecond to several seconds


Multi-nuclear operations (1H, 19F);


Fully automated acquisition of NMRD profiles


Temperature control (range from
-140 °C to +140 °C with a 0.1 °C resolution)

Minumum costs

Minimum operating costs (no cryogenic gases neces-

Sample preparation

No complicated sample preparation required


Measures solids, liquids, liquid crystals, colloids, complex


It’s evident that no conventional NMR spectrometer can pro- duce such materials research, we witness an increasing in- terest in NMR relaxometry and,in particular, in variable-field relaxometry. All NMR studies exploiting nuclear relaxation indicate the convenience of measuring nuclear relaxation time (T1) as a function of the magnetic field Br in which they occur (NMRD profile).
Since such “dispersion” curves retrace essentially the distribution of molecular motions in terms of frequency (the so called spectral densities), they provide an unusually direct way to “sampling” such distributions. Quan- titative evaluations lead to important data about the inte- ractions which couple molecular motions with nuclear spins. In order to fully exploit information of variable field relaxo- metry, the relaxation field values should cover a range of 4-5 orders of magnitude.
More over measurements in extremely low fields are particularly interesting since they reflect very slow motions and one would like to cover, in a single expe- riment, field values ranging from a few kHz to tens of MHz (Proton Larmor frequency).

FFC NMRD profiles used for QC of food


In the basic NMR Field Cycling experiment the Zeeman field B0', which is applied to the sample, is cycling through three different values. In the first period, a high magnetic field Bpol (polarization field) is applied to pre-polarize the sample in order to boost signal intensity.

Thereafter, the sample is al- lowed to relax in a second field Brelax (relaxation field) which can be set to any desired value, including zero. In the last period the field is set to the detection field Bacq for signal ac- quisition.

Schematic representation of the field cycling technique


Stelar’s FFC relaxometer, SMARTracer is a NMR instrument designed to measure the field dependence of NMR spin-lattice and spin-spin relaxation time T1 (Nuclear Magnetic Relaxation Dispersion – NMRD – profiles), from 10 kHz to a maximum operating magnetic field of 10 MHz (1H Larmor frequency units).

Instrument highlights:

– Minimum operating costs (no use of cryogen).

– Efficient and accurate temperature controller (−140 to +140°C with 0.1°C resolution).

– Research grade versatility (Stelar PC-NMR digital NMR Console).

– Simplicity of use (fully automated acquisition of T1 NMRD profiles).

SMARTracer consists of five different units, each one containing several subsystems. Units and subunits are listed below

  1. VTC90 Variable Temperature Control (VTC) unit for sample temperature control in a wide temperature range (-140°C to140°C)

  2. PC-NMR CONSOLE . The console includes

    • input/output devices

    • RF power transmitter

    • digital receiver and filters

    • RF front-end and preamplifier.

  3. Magnet Power Supply that includes the following subunits

    • Power MOSFET Banks

    • Reference and Field Regulation units

    • Interlocks system

    • Current and Magnet temperature display

    • Magnet temperature compensation system

  4. Cooling/Circulation System

    • Cooling system controller

    • Magnet liquid cooling pump

    • Cooling liquid tank reservoir

    • Cooling liquids, heat exchanger

  5. Magnet and Probe • Magnet

    • Probe and air flow temperature heater/sensor

    • Preamplifier and RF front-end box


Resistive, low inductivity, 2 layers air-core solenoid, suitable for Fast Field Cycling NMR measurements. The magnet is housed into a special glass-Perspex container and percolated by a special cooling liquid.

Access bore: 18 mm.

Max Field Bo: 0.25 Tesla +/-5%

Homogeneity: < 100 ppm over 1cm3

Field slew rate: < 1ms+ 200 us * MHz,


High stability computer
means of external parallel port and TTL lines.

Max. Power: 1.3kW

Max. Current: 130 A

Max voltage: 14 Vdc

Current stability: <100ppm

Switchable levels: 4 levels (off, Bpol, Brelax, Bacq) each level is software controlled

Switching time: < 1ms+ 200 us * MHz

Mains: Single phase 230 VAC / 1.3 kW 50/60 Hz


The magnet/power supply cooling unit implements dual independent, thermally coupled loops, one high pressure pump and very high efficiency heat exchanger between tap water and the cooling liquid. The secondary is a closed circuit using a cooling fluid at room temperature. The primary circuit uses tap water or dedicated chiller.

In case of use of tap water, filters are commanded.
– Maximum power dissipation is approx. 1.3 kW depending on water temperature and flow.
– Secondary cooling liquid – Min water request: Galden SV110

– Min water request: 300 l/hr of water at 12°C (1 bar) at maximum power

PC- NMR console

PC-NMR (Personal NMR Console) is the Stelar high performance, general purpose, NMR console. Its innovative design, besides Field Cycling Relaxometry, provides a single and powerful solution also for most NMR and NQR technique. The console includes input/output devices, RF power transmitter, digital receiver, RF front-end and preamplifier.
A powerful NMR software package with a sequence/experiment library is supplied. The system is housed in a 3U/19” rack.

Main features:
– n.4 (four) independent RF TX channels programmable from DC to 130MHz. Channel 1 is the default TX RF channel. Channels 2, 3 and 4 can be singularly and separately configured as additional RF channels or as DC outputs to drive external Gradients.
– The console features a digital receiver for direct acquisition of NMR signal from 500 KHz to 130MHz with a maximum spectral width of 10 MHz with data accumulation in 4 separate buffers or real and imaginary parts and phase and absolute value.
– The system implements a 128bit/20ns/7loops levels pulser.
– 250 W RF linear power pulse transmitter from 500KHz to 150 MHz

VTC90 Sample temperature controller

Standard Gas flow system

Range*: −140 to +140°C

Precision and stability: 0.1°C Gas Flow: 1000 l/hr at 1-3 atm, dehumidified and filtered.

* This is range of temperature that can be controlled by the unit the real temperature range that can be achieved at sample position strongly depends on dewar glass and probe and imput temperature of gas.

1. How far the instrument must be away from other magnetic resonance spectrometers – NMR and/or EPR. Is there any problem if both instruments are ON at the same time?
It is better not to keep the FCNMR relaxometer close to other super-con magnets. SMARTracer must be away from the other Super Con magnets or there must be a very good magnetic shield to reduce the environmental fields which comes from the super-con magnets. Refer to the data sheet provided by the manufacturer of super-con magnet and remember that fringe field from external sources (like super-con magnets) influences only at minimum measuring field in SMARTracer. Yes, the problem could exist only if both the instruments are ON at the same time.


2. How far the fringe field extends from SMARTracer?

The fringe field from SMARTracer extends to a very small distance (at 100cm, Bo is < 0.25 Gauss at 0.25 T working field). As a general rule, it’s the SMARTracer that can be disturbed by external fields from HR spectrometer not vice-versa.


3. What kind of temperature controller is used for samples in SMARTracer?

We use a standard gas flow system. Total range of the controlled temperature is ranging from –140 °C to 140 °C.
For temperature above temperature room, either dry air or Nitrogen gas is needed to control the temperature with flow of about 1000l/hr at 1atm. For lower temperature a system working with an evaporator of Liquid nitrogen can be supplied.


4. How versatile the instrument is?. What sample size is required? How long does an experimental run take, say for protons with a single peak getting 20 or 30 fields?
This relaxometer is designed to measure T1 (T2 also with limitation) of liquid as well as solid samples. User can do the experiment on samples with T1’s typically between fractions of ms to several tens of seconds. The Sample should be prepared in “10mm standard NMR tube” and optimal volume is about 1cc. The duration of the experiment depends on T1, number of averages, duty cycle and few other parameters. For example, for 2mM MnCl2 water solution (T1 at 10kHz is 8ms and at 10MHz is 40ms), only few minutes are necessary to record a complete profile with 30 points (i.e., 30 fields).


5. Is it possible to measure T2 and its field dependence with the SMARTracer ?
Yes with limitations. Thanks to some new concept introduced with the latest SMARTracer it’s now possible to measure the Hanh-Echo decay as a function of the magnetic field and trace the dependence of the Echo decay on the magnetic field in the full range allowed by the ralxometer (ask for specific documentation on this capability)
Moreover it’s possible to use SMARTracer for real T2 measurements at acquisition field, inside the tuning range of probe and field (4 – 10 MHz) (in proton Larmor frequency) running standard CPMG or SpinEcho or any other more advanced sequences by tuning the probe to different detection fields. In this case T2 is measured at the detection field using short echo-delay < 100us or less.
The Stelar SMARTracer is a variable field and variable frequency NMR system so that the most important advantage is that the measuring field can be set at any value inside the field range of the magnet.
In any traditional T2 experiment at fixed field the lowest frequency is mainly limited by the sensitivity, while the highest measuring frequency of T2 is limited by the maximum field of magnet.
On the purpose of measuring T2 at very low field, where sensitivity becomes the limit for classical method, it’s now possible to perform Field Cycling T2* measurements using a FC-Hahn-echo (Filed cycling modified experiment). Ask for more details.

6. What about the repeatability as well as accuracy in T1 over field strength?
Accuracy in T1 over field strength depends on the sensitivity of sample, number of scans, relaxivity of sample etc… By using 1cc 2mM MnCl2 water solution sample (one of our standard samples), the accuracy in T1 calculation over the field range (0.01to 10 MHz) is better than 1 % in only one scan in the complete NMRD profile acquired. The repeatability error in T1 is lower than 2 %.

7. What kind of resolution do you get for solid/biomolecules? Is the resolution determined by the observe field, or are there complications in determining the quality of the spectrum obtainable?
SMARtracer does not acquire spectra as in HR NMR. The FC measurement is based on a pure T1 experiment which is observing evolution (in time domain) of the magnetization of the observed nucleus. There could be one or more contributions to the T1 and these different contributions correspond to different motions. Information about molecular dynamics of the bio – molecules can be obtained in this way. Field homogeneity is not the main demand in FC. Also, we have to consider that the observing field would too low to get any kind of useful spectral resolution, even with very good homogeneity of the magnet.

8. Is it easy to change the pulse sequence parameters and write a new pulse sequence?
Yes. It’s very easy to change/modify/edit the pulse sequence parameters as well as writing a new pulse sequence. The Pulse Sequence Script manual explains the basics followed in a pulse sequence.
After going through the manual, users can easily write their own pulse sequence.
The pulser/sequencer of PC-NMR allows to design theoretically any experiments. Part of channels are used to control the timing of complex RF pulses and external events. Several pulses are available to trigger external devices (such UV lamp etc..).
At present the NMR pulse sequence can be written for any number of pulses delays in a sequence. The length, amplitude, phase of each pulse can be fully programmable separately in the sequence. User can edit/write a pulse sequence using any standard ASCII text editor.


9. How easily one can switch from one type of experiment to another?
To switch from one type of experiment to another you need just to load the correct one from the folder where all the experiments are collected.

10. Does the possibility exist to run a couple of test samples on your instrument?
Yes. We will be very happy to receive your samples for some test measurements. Please be in contact with us.

11. How do you provide service? What is Stelar policy I’m concerned about this:
Stelar is servicing SMARTracer installations around the world from his factory in Italy. It is our experience that factory supported service is at present the best for customers for the following reasons:

a) Service and maintenance of the system as well as all other technical support to the customer is usually done by the same engineer who has provided installation and training, which becomes for the user the reference for any technical problems. It is our opinion that this approach is the most efficient and cost effective way to give technical support to the customer.

b) Included in the instrument price is a training period for one technician or engineer identified by the customer from his staff. The training is conducted at the Stelar facility in Italy during the final tests, just before the delivery of the instrument. The objective of the training is to prepare the selected individual on all main service and maintenance problems and procedures of the SMARTracer. The factory service training offers the following benefits to the customer:
– 1) One person in your laboratory will be knowledgeable of both hardware and software of the instrument. This knowledge will contribute to maintaining the system with optimum throughput and quality of data.
– 2) The trained person could act as an interface with Stelar for a fast line and reliable analysis of problems caused by any failure or operator error in using the instrument.
– 3) Effective training can drastically reduce the number of interventions for service and save on the cost of out of warranty service.

c) Provided with SMARTracer are software tools for failure diagnosis and hardware performance evaluation for all main functional blocks of the instrument. This is extremely helpful for a fast search and identification of problem/failure issues.

d) A kit of spare parts and components is included in the SMARTracer deliverables.


Yes. We will be very happy to receive your samples for some test measurements.

Please be in contact with us.