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Code Block
titleConnecting to JET - instructions
collapsetrue
In order to access the new mdsplus.jetdata.eu service, users will need to make a minor change to their codes, changing the host parameter 
in the connection calls from "mdsplus.jet.efda.org" or "mdsplus.jet.uk" to "ssh://<username>@mdsplus.jetdata.eu" 
where <username> is the your JET account username (e.g. jsmith or xy1234)

Users will also need to register their SSH public key with us in order for this to work. 
Please do this by emailing support@it.ukaea.uk with the subject line “MDSplus SSH Key Registration”. 
Please put your SSH Public key into the body of the message – do not add attachments to the email. 
It is important that you provide your public key only and do not include your private key (users should take all reasonable steps to protect their private keys). 
(Due to a limitation of the mdsplus server, please avoid using Ed25519 keys, though ecdsa keys can be used)

Suggested email text to use:

Please register my SSH Public key for use with mdsplus.jetdata.eu. 
My username is : <your shortname>
My SSH Public key is: 

Once your key has been registered we will confirm this back to you and you will then be able to test the connection and your clients

If you need information about creating SSH keys please see the information here:
•	There is some general information here: https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys-2
•	There is a page on how to create key pairs with openssh at https://www.ssh.com/academy/ssh/keygen
•	There is a page on how to create key pairs with putty at https://www.ssh.com/academy/ssh/putty/windows/puttygen
•	The www.ssh.com has pages about generating keys for other ssh clients too.

Important Note: when generating SSH key pairs, we’d suggest that most users will find it more convenient not to use a passphrase (i.e. leave it blank). 
Also, due to a limitation of the mdsplus server, please avoid using Ed25519 keys, though ecdsa keys can be used


Once the pair of keys 'id_rsa_jet'  is created it necessary that the system can distinguish between the keys. You can inform the system by editing 'config' file in ~/ .ssh folder.

Code Block
titlessh config
Host jet
 HostName mdsplus.jetdata.eu
 User <your jet username>
 IdentityFile ~/.ssh/id_rsa_jet

In an example we fetch JET data  (dda='hrts', uid = 'jetppf', seq=0, dtype= ['TE', 'DTE', 'NE', 'DNE', 'Z']) .

Example of script fetching HRTS JET data.

Code Block
titleExample script of fetching data from JET
linenumberstrue
collapsetrue
#example of saving experimental data to ids

import os
import json	

def read_ppf(conn, shot, ppf, seq=0, uid='jetppf',debug=False):
    ierr = conn.get('_sig=ppfuid("' + uid +'")')
    c = '_sig=jet("ppf/%s/%d",%d)'% (ppf, seq, shot)
    if debug: print('\nDEBUG: %s\n' % c)
    try:
        s = conn.get(c)
        raw = s.data()
        dim0 = conn.get('dim_of(_sig,0)').data()
        try:
          dim1 = conn.get('dim_of(_sig,1)').data()
          return {'raw': raw, 'x':dim0, 't':dim1}
        except:
          return {'raw': raw, 't':dim0}
    except:
      return None


def readExperimental(data_exp, host, server='ssh://'):
    '''
    reads experimental data after connecting to the host via ssh server
    data_exp: data details in dictionary format	
    '''
    import sys
    try:	
        import MDSplus
        haveMDS = True
    except:
        print(' No MDSplus support found.\n')
        print('\n\n\n Exiting...\n')
        exit(1)

    try:
      conn = MDSplus.Connection(server+host)
      print('Connection OK')
      connected = True
    except:
      print('in readExperimental, MDSplus failed: ',sys.exc_info()[1])
      connected = False

    if connected:
        try:
            EXP={}
            for sig in data_exp['dtype']:
                print('reading dtype: ',sig)
                signal= data_exp['dda']+'/'+sig
                aux = read_ppf(conn, discharge, signal, seq=data_exp['seq'], uid=data_exp['uid']) 
                # Z coordinate is one dimensional, aux['raw'] is 2D by default
                if sig=='Z':
                    aux['raw'] = aux['raw'].flatten()

                EXP[sig] =  {
                    'time': aux['t'].tolist(),
                    'x':aux['x'].tolist(),
                    'data': aux['raw'].tolist(),
                    'signal': signal 
                    }
        except:
            print('in readExperimental, read_ppf failed: ',sys.exc_info()[1])
            return None
        del(conn)
    else:
        EXP=None
    
    return EXP

###########


host='jet'

discharge=99357

# data to download
data={}
data['dda']='hrts'
data['uid'] = 'jetppf'
data['seq']=0
data['dtype']=['TE','DTE','NE','DNE','Z']

EXP=readExperimental(data,host)

if EXP:
    a_file = open('data_jet_fetched_'+str(discharge)+'_'+data['dda']+'_'+str(data['seq'])+'.json', "w")
    json.dump(EXP, a_file)
    a_file.close()


IMAS UDA

It is possible to access and fetch and map data from several  experiments WEST, JET , TCV and AUG using UDA protocol which id described in detailed on ITER confulence pages (requires iter account). Accessing data with UDA needs to be adapted due to recent (Aug 2021) change in connection protocol.

Saving data to IMAS

Before saving the experimental data to imas it is important check which version of imas data dictonary we are using.

...

Note: channel[i1].position.r and channel[i1].position.z are scalars.

Let's assume we want to save measured HRTS profiles of electron temperature and density with errors for the JET shot 99357. for the JET shot 99357. 

After fetching data from JET (dda='hrts', uid = 'jetppf', seq=0, dtype= ['TE', 'DTE', 'NE', 'DNE', 'Z']) After fetching data from JET we saved it in a dictionary with the following structure:

...

'data' array consist of 701 time slices (from around t=40s to t=75s) and 63 experimental points. We need to project data onto numpy arrays:

Code Block
titlesaving to imas
import json
import imas,os,datetime,sys
import getpass
import numpy as np
from imas import imasdef
 

db = 'data_access_tutorial'
shot=99357 
run=1

#creates the Data Entry object 'data_entry', a kind of handler of the pulse file with sho, run, belonging to database 'data_access_tutorial' of the current user, using the MDS+ backend
data_entry = imas.DBEntry(imasdef.MDSPLUS_BACKEND, db, shot, run, user_name=getpass.getuser())
#data_entry = imas.DBEntry(imasdef.HDF5_BACKEND, db, shot, run, user_name=getpass.getuser())
# Open save data_entry to data base

# Tries to open data_entry
op = data_entry.open()
#if fails, creates one
op = data_entry.open()
#open() and create(0 return a tuple (x_int,y_int) where x<0, y>0, x number of failures, y number of successes in the current session. 
#if open fails, create data_entry
if op[0]<0:
     cp=data_entry.create()
     if cp[0]==0:
        print("data entry created")
elif op[0]==0:
    print("data entry opened")	

# Fetched data Open file with fetched data, the data is not numpy array format
with open("data/data_jet_hrts_99357.json") as json_file:
    hrts=json.load(json_file)

x_coord=np.array(hrts['TE']['x'])
# no. of space points
nb_points = len(x_coord)
#no of time slices
nb_slices=len(hrts['TE']['time'])

#here, we can perform some read/write operations using the get/put() operations
#...

#creating the 'thomson_scattering' auxiliary IDS and initializing it
thomson = imas.thomson_scattering() #creates a 'thomson scattering' IDS
thomson.ids_properties.homogeneous_time=1 #setting the homogeneous time (mandatory)	
thomson.ids_properties.comment='IDS created for testing the IMAS Data Access layer' #setting the ids_properties.comment attribute
#thomson.time=np.array([0.]) #the time(vector) basis must be not empty if homogeneous_time==1 otherwise an error will occur at runtime

# since all data is available we can save whole time vector at once
thomson.time=np.array(hrts['TE']['time'])

thomson.ids_properties.creation_date = datetime.datetime.now().strftime("%y-%m-%d")

%m-%d")
# the number of channel corresponds to number of data points
thomson.channel.resize(nb_points)

for j in range(nb_points):
    thomson.channel[j].t_e.data.resize(1)
    thomson.channel[j].t_e.data_error_upper.resize(1)
    thomson.channel[j].n_e.data.resize(1)
    thomson.channel[j].n_e.data_error_upper.resize(1)

# python interface accepts only numpy arrays to be saved in ids
te_data = np.array(hrts['TE']['data']) #2D
dte_data = np.array(hrts['DTE']['data'])#2D
ne_data = np.array(hrts['NE']['data'])#2D
dne_data = np.array(hrts['DNE']['data'])#2D	
z_data = np.array(hrts['Z']['data']) #1D
r_data = np.array(hrts['TE']['x']) #1D
	
for j in range(nb_points):
    thomson.channel[j].position.r=r_data[j]
    thomson.channel[j].position.z=z_data[j] 
    thomson.channel[j].t_e.data=te_data[:,j]
    thomson.channel[j].t_e.data_error_upper=dte_data[:,j]
    thomson.channel[j].n_e.data=ne_data[:,j]
    thomson.channel[j].n_e.data_error_upper=dne_data[:,j]

sequence = hrts['TE']['seq'] 
data_entry.put(thomson,seq)# the last number is the occurence which can be used to store the data sequence number
#closing the Data Entry
data_entry.close()  

Note, that we used (once and outside the loop) only one command 'data_entry.put(thomson)' to save the data once outside the loop. Since we had all data available at once we didn't need to use put and putSlice commands to save time slice by time slice. However, the two approaches should be equivalent and provide the same ids. The first one is faster as procedure of saving the data in the data physical memory is called performed only once.

If the data was saved with MDSPLUS backend , the shot number is included in the data files names and is saved in the following folder:

...