Singular

Only the usual usuel latin letters, the @, integers, the underscore _ , and ( ) for indeced variables are allowed.
This gives a great variety to name the objects:
[code]
> ring rr = 0,(x1,x_2,x(3)),dp;
> maxideal(1)^2;
_[1]=x1^2
_[2]=x1*x_2
_[3]=x1*x(3)
_[4]=x_2^2
_[5]=x_2*x(3)
_[6]=x(3)^2

> ring rgreek = 0,(alpha,beta,gamma),dp;
> maxideal(1)^2;
_[1]=alpha^2
_[2]=alpha*beta
_[3]=alpha*gamma
_[4]=beta^2
_[5]=beta*gamma
_[6]=gamma^2
[/code]

I'm trying to use Greek characters in Singular, but it's giving me an error. Is there any way to make this work or is there some other implementation of Greek characters in Singular? My main concern is with having more variables than there are letters in the alphabet, and if there are other solutions to this problem I would welcome those too. Thanks!
[code]
R = singular.ring(0,'(Ψ,Ω,α)','ds')
---------------------------------------------------------------------------
SingularError Traceback (most recent call last)
<ipython-input-361-30b6da8019fd> in <module>()
----> 1 R = singular.ring(Integer(0),'(Ψ,Ω,α)','ds')

/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/interfaces/singular.pyc in ring(self, char, vars, order, check)
1049 s = '; '.join(['if(defined(%s)>0){kill %s;};'%(x,x)
1050 for x in vars[1:-1].split(',')])
-> 1051 self.eval(s)
1052
1053 if check and isinstance(char, integer_types + (sage.rings.integer.Integer,)):

/opt/sagemath-8.6/local/lib/python2.7/site-packages/sage/interfaces/singular.pyc in eval(self, x, allow_semicolon, strip, **kwds)
658 # Singular actually does use that string
659 if s.find("error occurred") != -1 or s.find("Segment fault") != -1:
--> 660 raise SingularError('Singular error:\n%s'%s)
661
662 if get_verbose() > 0:

SingularError: Singular error:
? `N` is not defined
? error occurred in or before STDIN line 12791: `(N()>0){kill N(;};; if(defined(N))>0){kill N);};; if(defined(N1)>0){kill N1;};`
? error occurred in or before STDIN line 12791: `(N()>0){kill N(;};; if(defined(N))>0){kill N);};; if(defined(N1)>0){kill N1;};`
? last reserved name was `defined`
skipping text from `0`
[/code]